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Chronic Myelocytic Leukemia

Chronic myelocytic leukemia

Definition

Chronic myelocytic leukemia (CML) is a cancer of white blood cells in which too many white blood cells are made in the bone marrow. Chronic myelogenous leukemia and chronic myeloid leukemia are other names for CML and refer to the identical disease. In CML, there is an increased proliferation of white blood cells called granulocytes.

Description

Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called "blasts" or "stem cells" that mature into different types of blood cells. Unlike acute leukemias, in which the process of maturation of the blast cells is interrupted, in chronic leukemias, the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.

The different types of cells produced in the bone marrow are red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and platelets, which play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: the granulocytes, monocytes, and the lymphocytes.

The granulocytes, as their name suggests, have granules (particles) inside them. These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are also important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. There are two main types of lymphocytes: T lymphocytes and B lymphocytes. They have different functions within the immune system. The B cells protect the body by making antibodies. Antibodies are proteins that can attach to the surfaces of bacteria and viruses. This attachment sends signals to many other cell types to come and destroy the antibody-coated organism. The T cell protects the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. The T cells can recognize these proteins and produce certain chemicals (cytokines) that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

Chronic leukemias develop very gradually. The abnormal lymphocytes multiply slowly, but in a poorly regulated manner. They live much longer than normal cells and thus their numbers build up in the body. The two types of chronic leukemias can be easily distinguished under the microscope. Chronic lymphocytic leukemia (CLL) involves the T or B lymphocytes. In chronic myelocytic leukemia (CML), the cells affected are the granulocytes. In addition, CML involves abnormalities of both the blood platelets, structures that help blood to clot, and the red blood cells, the blood cells that carry oxygen.

Very rarely will CML appear in children. Juvenile CML is a distinct disease of children younger than 14 years of age. There is a decrease in the number of blood platelets, substances that help the blood to clot. And there is an increase in certain white blood cells.

Demographics

Slightly more men than women are affected by CML. The average patient is between 50 and 60 years of age. However, CML can affect people of any age. Chronic leukemias account for 1.2% of all cancers. Chronic myelocytic leukemia is generally seen in people in their mid-40s. According to the estimates of the American Cancer Society (ACS), approximately 4, 400 new cases of leukemia were diagnosed in the year 2000, 2, 600 in men and 1, 800 in women. Between 1973 and 1991, the rate at which CML appeared in the United States decreased slightly.

Causes and symptoms

People exposed to nuclear and other radiation are at increased risk for CML. Thus, people who have had higher exposure to radiation for medical reasons are at increased risk of developing this cancer. Parents with CML do not have children who are more than normally likely to develop CML. However, it is possible that people whose immune system exhibits certain characteristics are at increased risk for the disease.

CML develops in a two-or three-stage progression. First, the chronic phase appears. Between 60 and 80 percent of patients next exhibit the symptoms of what is called the accelerated phase. The final stage of CML is the terminal blastic phase.

Symptoms of chronic phase CML appear in 60%-85% of patients. This means 15% to 40% of all the people diagnosed with CML have no symptoms at all and are diagnosed with the disease only because of the results of a routine blood test. Patients who do have symptoms most frequently find themselves to have fatigue , weight loss , or pain. Some patients have a mass of tissue or an enlarged liver that the doctor is able to feel. Some patients experience strokes, visual problems, a lowering of alertness or responsiveness, priapism, and ringing in the ear. Many patients in accelerated phase CML have no specific symptoms. However, fever , weight loss, and night sweats may appear.

Patients with terminal, blastic phase CML often experience symptoms. There may be fever, weight loss, night sweats, and bone pain . Many patients develop infections. Many have anemia (low counts of red blood cells) and many bleed easily.

Diagnosis

There are no screening tests available for chronic leukemias. The detection of these diseases may occur by chance during a routine physical examination.

People who have CML have an unusually high number of white blood cells. Somewhat less than half of these people also have high numbers of blood platelets. Most patients have mild anemia. The composition of the bone marrow in CML patients also differs from that of a healthy person. The marrow is described as being hyper-cellular. This means that the number of cells present in the bone marrow is unusually great.

If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, an enlarged liver or spleen, bruises, or pinpoint red rashes all over the body are among the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood.

Standard imaging tests such as x rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other organs of the body, such as the bones, chest, kidneys, abdomen, or brain.

Many doctors consider the presence of the Philadelphia (Ph) chromosome to be a crucial factor in the diagnosis of CML. The Ph chromosome is formed if some of the genetic material in two specific parts of two specific genetic units, called chromosomes, have exchanged some content in a particular way and created an arrangement of genetic material characteristic of CML patients.

Laboratory findings indicate when a patient enters the accelerated phase of CML. There may be more than 15% blasts (immature cells) in the blood. Alternately, the accelerated phase has started when more than 30% of the blood may be composed of a combination of blasts and promyelocytes. Promyelocytes are immature granulocytes. Another marker for the start of the accelerated phase is when the blood contains more than 20% of another white blood cell, called a basophil. Finally, the accelerated phase may be heralded by there being more than 100, 000, 000, 000 platelets per liter of blood. The terminal, blastic phase of CML is heralded by measurements of 30% or more of blasts in either the bone marrow or the blood.

Clinical staging, treatments, and prognosis

Staging

Several different staging systems are in use. Most of these make use of the fact that a number of factors relevant to patients with CML say something about the patient's prognosis. Among these factors are the patient's age, the white blood cell count, the platelet count, the percentage of blast cells and basophil cells in either the blood or the bone marrow, the size of the liver, the size of the spleen, population of red blood cells that have a central portion called a nucleus, and the evolution of certain cell clones.

Treatment

It is very fortunate that several years ago the American Society of Hematology convened an Expert Panel on Chronic Myeloid Leukemia. This panel reviewed available therapies and published its findings in 1999. The findings were rigorously based upon evidence provided by the best research. The panel, comprised of top doctors from around the world, carefully sifted through all of the studies on treatment for CML and put aside all those studies performed with questionable methodology. This is a most important document relevant to CML therapy.

Since the publication of the findings of the expert panel, however, a new medicine has demonstrated great success in studies. This new medicine is known as STI571, Imatinib mesylate , or Gleevec. Since Gleevec was such a new drug in 2001, few studies have been conducted to evaluate its long-term effects. Furthermore, researchers have not had an opportunity to view the effects of imatinib mesylate over a period of five, 10, or 20 years.

In terms of CML therapy, the situation in 2001 was the following: physicians have the reliable report of the Expert Panel and a little bit of new information about a new medication. How the Expert Panel's findings and this new information should be integrated with the results of recent studies of imatinib mesylate is an issue that cancer doctors are currently resolving.

The Expert Panel looked at treatment of the chronic phase of CML. One therapy examined by the panel is busulfan (BUS). Another is hydroxyurea (HU). Both BUS and HU are chemotherapy medications. Studies have demonstrated that CML patients in chronic phase given HU live longer than patients given BUS.

Another therapy examined by the expert panel is interferon-alpha. Interferon is a chemical normally made in the cells of the body. It helps protect the body against viruses and also seems to have some effect against certain cancers. The interferon used as medicine is a laboratory-manufactured copy of the interferon produced by the body. The Expert Panel concluded that patients in chronic phase CML who have received interferon live longer than those given HU or BUS. This conclusion applies, in particular, to patients who have had little prior treatment for CML, who start interferon treatment soon after diagnosis, and who have certain other characteristics. However, side effects of interferon therapy are greater than those of therapy with HU or BUS. Patients who develop the side effects of interferon may feel like they have the flu. Patients receiving interferon seem to do better if they also receive chemotherapy with either HU or a medicine called Ara-C, or cytarabine .

Bone marrow transplantation (BMT) is an effective treatment for CML. In BMT, the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from another person (donor) whose tissue is either the same or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy . To replace the destroyed marrow, healthy marrow from the donor is given to the patient.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is then destroyed with high dose chemotherapy and radiation therapy. Following that, the patient's own marrow that was frozen is thawed and given back to the patient.

Allogeneic BMT may be used soon after diagnosis or after a patient has been treated with interferon or chemotherapy. The Expert Panel found that carefully designed, well-controlled, randomized studies have not been conducted on BMT therapy for CML. In the studies that do exist, scientists performed BMT on a group of patients and then observed the results. These studies show that BMT may lead to long-term remission. Remission is achieved if the disease becomes diminished for a period. Patients appear to live longer if they received chemotherapy followed by BMT. But the Expert Panel cautions that the results of these observational studies cannot be relied upon. One problem with them might be, for example, that the patients chosen to receive BMT might have started out being healthier than patients who did not receive BMT. The side effects of BMT may be severe, and a large number of CML patients receiving BMT die as a direct result of the BMT.

Therefore, one important consideration when BMT is being considered is whether the conditions under which the individual patient might receive BMT are favorable. In other words, is a very suitable marrow donor available? Is the patient within two years of CML diagnosis? It is important that patients understand clearly the ptential benefits and risks of BMT. One comment made by the Expert Panel is that younger patients who hope to live a very long time after CML diagnosis are more likely to benefit from allogeneic BMT. Autologous BMT has not achieved superior long-term results.

The recent studies of imatinib mesylate found it very effective in two groups of CML patients. One group was made up of patients who had unsuccessful results with interferon alfa therapy. The other group of CML patients studied were in the blast phase of the disease. Both studies found the medication to be effective and well tolerated. However, studies reporting on the effectiveness of imatinib mesylate over periods of five years or longer were not yet available in 2001.

Because leukemia cells can spread to all the organs via the blood stream and the lymph vessels, surgery is not considered an option for treating the leukemias.

The Expert Panel was careful to state that patient preferences should be taken into account as a treatment plan is developed. No approach to CML therapy is perfect. Each provides some benefit and is accompanied by certain side effects and risks. Which therapy or therapies is best for each individual patient depends upon on certain facts, such as the age of the patient and whether the patient is suffering from illnesses other than CML. In addition, the Expert Panel explains that the personal preferences of each patient are an important consideration. For example, some patients would rather avoid potential severe side effects and would be willing to give up the potential of living another few months or years. Other patients would be entirely unwilling to accept this way of looking at risks and benefits. It is important that health care professionals educate patients as to what treatment options are available and the perfections and imperfections associated with each. The opinions of each patient should be an important factor in deciding which treatment is best for that patient.

In the accelerated and blastic phase of CML, aggressive chemotherapy may be given. Combination chemotherapy, in which multiple drugs are used, is more effective than using a single drug for the treatment. Interferon and BMT may be used, although results are not as good as for patients in the chronic phase of CML.

It should be mentioned that during treatment the doctor may order a procedure called leukapheresis. This lowers the numbers of white blood cells circulating in the patient's body. Also, either before or after therapy, it may be necessary to provide the patient with a transfusion of blood platelets. In addition, antibiotics are often used to help prevent infection in leukemia patients.

Prognosis

The most important factor in determining the likelihood that a patient receiving interferon therapy will achieve long-term survival is whether there is a positive response to interferon-alfa. Although experience with imatinib mesylate is being gathered in studies, this drug remains so new that doctors do not know what effect it will have on the prognosis of CML patients. Once the threat of transplantation-related complications has passed, patients receiving BMT may achieve longer survival than patients receiving interferon therapy.

Before the discovery of modern therapies, patients often spent between three-and-a-half and five years in the chronic phase. Then some patients entered an accelerated phase, from which most died within 18 months. Once patients were in the terminal, blastic phase most died within six months. However, all of this has changed with the arrival of newer therapeutic techniques. Just as many patients used to die from heart attack while similar patients may now live for decades, so cancer patients are achieving longer lives.

Coping with cancer treatment

Cancer patients need supportive care to help them come through the treatment period with physical and emotional strength in tact. Many patients experience feelings of depression , anxiety, and fatigue, and many experience nausea and vomiting during treatment. Studies have shown that these can be managed effectively if discussed with the doctor.

Prevention

Although some cancers are related to known risk factors, such as smoking, in leukemias, there are no definitive risk factors. Therefore, at the present time, there is no way known to prevent the leukemias from developing. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation, the organic liquid benzene, or people who have a history of other cancers of the lymphoid system (Hodgkin's lymphoma) should undergo periodic medical checkups.

See Also Chromosome rearrangements

Resources

BOOKS

Braunwald, Eugene, et al. Harrison's Principles of Internal Medicine, 15th ed. New York: McGraw-Hill, 2001.

deWitt, Susan C. Essentials of Medical-Surgical Nursing, 4th ed. Philadelphia: W. B. Saunders, 1998.

Humes, H. David, et al. Kelley's Textbook of Internal Medicine, 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.

Pazdur, Richard, et al. Cancer Management: A Multidisciplinary Approach: Medical, Surgical, & Radiation Oncology, 4th ed. Melville, NY: PRR, 2000.

Souhami, Robert, Jeffrey Tobias. Cancer and Its Management, 3rd ed. London: Blackwell Science, 1998.

PERIODICALS

Drucker, B. J., et al. "Efficacy and safety of a specific inhibitor of the BCR-ABL tyrosine kinase in chronic myeloid leukemia." New England Journal of Medicine, 344 (2001): 1031-1037.

Drucker B. J., et al. "Activity of a specific inhibitor of the BCR-ABL tyrosine kinase in the blast crisis of chronic myeloid leukemia and acute lymphoblastic leukemia with the Philadelphia chromosome." New England Journal of Medicine, 344 (2001): 1038-1042.

Silver, Richard T., et al. "An evidence-based analysis of the effect of busulfan, hydroxyurea, interferon, and allogeneic bone marrow transplantation in treating the chronic phase of chronic myeloid leukemia: developed for the American Society of Hematology." Blood, 94 (1999): 1517-1536.

ORGANIZATIONS

The National Cancer Institute publishes useful texts available through the Internet or by mail, and answers questions by telephone. Some publications include: Leukemia, What You Need to Know About Leukemia, PDQ -Treatment -Patients: Chronic Myelogenous Leukemia, and Complementary & Alternative Therapies for Leukemia, Lymphoma, Hodgkin's Disease, & Myeloma. Telephone: 1-800-4CANCER. Web site: <www.nci.nih.gov/>.

The Leukemia & Lymphoma Society (Formerly Leukemia Society of America) publishes useful texts available through the Internet or by mail. Some publications include: Chronic Myelogenous Leukemia (CML), Choosing a Specialist. Choosing a Treatment Facility, Making Intelligent Choices About Therapy, Understanding Blood Counts, Patient Aid Program, and Family Support Group. Telephone:1-800-955-4572. Web site: <www.leukemialymphoma.org/>.

The American Cancer Society publishes useful texts, which include: Adult Chronic Leukemia -Overview, Leukemia -Adult Chronic: Treatment, Leukemia -Adult Chronic: Detection and Symptoms, Leukemia: Adult Chronic FAQ [Frequently Asked Questions], and Leukemia -Adult Chronic: Prevention & Risk. Telephone:1-800-ACS-2345. Web site: <www.cancer.org/>.

National Coalition for Cancer Survivorship. 1010 Wayne Avenue, 7th Floor, Silver Spring, MD 20910-5600. Telephone: (301) 650-9127 and (877)NCCS-YES [877-622-7937). Web site: <www.cansearch.org>.

Lata Cherath, Ph.D.

Bob Kirsch

KEY TERMS

Accelerated phase

The middle one of the three-phase course of CML. However, between 20 and 40 percent of patients never enter the accelerated phase but, rather, go directly from the chronic to the terminal blastic phase.

Basophil

A type of white blood cell

Blast

An immature cell

Bone marrow

Spongy tissue found in the large bones of the body

Chemotherapy

Treatment with drugs that act against cancer.

Chronic phase

The initial phase of CML.

Hypercellular

Bone marrow is described as being hypercellular if the number of cells present in the bone marrow is unusually great.

Leukapheresis

A procedure to remove or extract excessive white blood cells from the blood.

Philadelphia (Ph) chromosome

The Philadelphia (Ph) chromosome is present if some of the genetic material in two specific parts of two specific genetic units, called chromosomes, have exchanged some content in a particular way.

Remission

Remission of a disease is achieved if the disease becomes diminished for a period.

Terminal blastic phase

The final stage of CML.

QUESTIONS TO ASK THE DOCTOR

  • How can I obtain supportive care so I come through this not only alive but with my family and emotional life intact?
  • What sort of benefit and what sort of side effects might each of the available treatment options bring?
  • Would you please inform me about the treatment options and let me tell you about the priorities in my life so I can participate in forming a treatment plan?
  • What is my prognosis?
  • Are blasts present?
  • Has complete remission or partial remission been achieved?
  • What can I do to lower my risk of infection during chemotherapy?

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Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia

Definition

Chronic lymphocytic leukemia (CLL) is a cancer of white blood cells. In CLL, mature white blood cells of certain types called lymphocytes function abnormally and cause disease.

Description

Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called "blasts" or "stem cells" that mature into different types of blood cells. Unlike acute leukemias, in which the process of maturation of the blast cells is interrupted, in chronic leukemias, most of the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.

The different types of cells produced in the bone marrow are red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body, and white blood cells (WBCs), which fight infection. Platelets play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: the granulocytes, monocytes, and the lymphocytes.

The granulocytes, as their name suggests, contain granules (particles). These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are the second type of white blood cell. They also are important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. There are two main types of lymphocytes: T lymphocytes and B lymphocytes. They have different functions within the immune system. The B cells protect the body by making "antibodies." Antibodies are proteins that can attach to the surfaces of bacteria and viruses. The occurrence of this attachment sends signals to many other cell types to travel through the blood and destroy the antibody-coated organism. The T cell protects the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. T cells recognize these proteins and produce certain chemicals (cytokines) capable of destroying the virus-infected cells. In addition, T cells destroy some types of cancer cells.

Chronic leukemias develop very gradually. The abnormal lymphocytes multiply slowly, and in a poorly regulated manner. These lymphocytes live much longer than normal lymphocytes and, thus, their numbers build up in the body. In CLL, lymphocytes accumulate. The enlarged lymphocyte population congregates in the blood, bone marrow, lymph nodes, spleen, and liver. The two types of chronic leukemias can be easily distinguished under the microscope. Chronic lymphocytic leukemia (CLL) involves the T or B lymphocytes. B-cell abnormalities are more common than T-cell abnormalities. T cells are affected in only 5% of the patients.

Demographics

Ninety percent of CLL cases are seen in people who are 50 years or older, with the average age at diagnosis being 65. Rarely is CLL diagnosed in a patient who is less than 35 years of age. The incidence of the disease increases with age. It is almost never seen in children. According to the estimates of the American Cancer Society (ACS), approximately 8, 100 new cases of CLL were diagnosed in 2000, 4, 600 in men and 3, 500 in women.

CLL affects both sexes. Among patients younger than 65, the disease is slightly more common in men. However, among patients older than 75 years of age, CLL appears almost equally in men and women. Within the United States, CLL affects African-Americans as frequently as it does Caucasians. However, CLL appears more frequently among Americans than among people living in Asia, Latin America, and Africa.

In the United States and Europe, CLL accounts for more than one-quarter of all diagnosed leukemias. Over the past 50 years, the rate at which CLL has been appearing has increased significantly. However, many doctors think that this increase is not necessarily due to the disease actually being more common than in the past, but instead due to the fact that the disease is now more likely to be diagnosed when it does appear. Fifty years ago, only one out of ten CLL patients was diagnosed during the early stages of the disease. Now, half of all CLL patients are diagnosed during this early stage.

Causes and symptoms

The cause of CLL is unknown. It is certain, however, that CLL is linked to genetic abnormalities and environmental factors. For example, close family members of patients with CLL are twice as likely to seven times as likely to be diagnosed with CLL as people in the general population. For another example, exposure to certain chemicals used in farming and other agricultural occupations may increase the risk that a person will develop CLL. In contrast, CLL is not associated with exposure to radiation known to cause other cancers. As of 2001, doctors were unsure whether people who have had certain virus infections are more likely to develop CLL than are people in the general population. If there does turn out to be such an association, it would not be with all viruses but with two human retroviruses (HTLV-I and HTLV-II) or with Epstein-Barr virus (EBV).

The symptoms of CLL are generally vague and non-specific. One out of five patients with CLL has no symptoms at all, and the disease is discovered only through a routine blood test. A patient may experience all or some of the following symptoms:

  • chronic fatigue
  • weakness
  • a general feeling of malaise or of things being not quite right
  • swollen lymph nodes
  • an enlarged spleen, which could make the patient complain of abdominal fullness
  • a general feeling of ill health
  • fever
  • frequent bacterial or viral infections.
  • unusually severe response to insect bites
  • night sweats
  • weight loss not due to dieting or exercise

Diagnosis

There is no screening test for CLL. If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. In addition, the doctor will look to see whether the liver and spleen are enlarged. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. Some authorities state that CLL may be diagnosed if the number of lymphocytes in the blood exceeds a certain level.

The doctor may perform a bone marrow aspiration and biopsy to confirm the diagnosis of leukemia. During the bone marrow biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hipbone. These samples are sent to the laboratory for examination. In many CLL patients, more than one-fourth of the bone marrow is made up of mature lymphocytes. In addition to diagnosis, bone marrow biopsy is also conducted during the treatment phase of the disease to see if the leukemia is responding to therapy.

Some CLL patients have a condition called hypogammaglobulinemia. Immunoglobulins are normal parts of the body's immune system, the system used to fight off infection. Patients with hypogammaglobulinemia have very low levels of all of the various types of immunoglobulins.

The doctor may also conduct immunophenotyping. This involves taking a sample of the blood and looking at what types of cells of the immune system are being affected by the CLL. Approximately 19 out of 20 CLL patients have the B-cell type of CLL. Far more rare is the T-cell type of CLL. In addition, the doctor may look for abnormalities in the chromosomes of the affected cells. Chromosomes are a unit of genetic material within cells. Patients exhibiting no chromosomal abnormalities have a better prognosis than those who do have such abnormalities. If the abnormalities become more complex over time, the patient's prognosis may worsen.

Standard imaging tests such as x rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other organs of the body, such as the bones, chest, kidneys, abdomen, or brain.

Clinical staging, treatments, and prognosis

Staging

Usually one of two systems are used to stage CLL. One of these is the Binet system and the other the Rai system. According to the Rai system, patients at low risk have no enlargement of lymph nodes, spleen or liver. The occurrence of these marks entry into the intermediate stage, according to Rai. High risk patients have, in addition, anemia and a significant decrease in the number of blood platelets in their blood. Blood platelets help blood to clot. According to the Binet system, a patient's stage depends upon how much hemoglobin (part of red blood cells that carry oxygen) and how many platelets are in the blood, as well as how many other areas the disease has affected. According to both systems, patients at low risk usually survive more than ten years. Patients at intermediate risk usually survive about six years. Patients at high risk usually survive about 2 years. Other factors with important implications for prognosis include the pattern at which bone marrow is being affected by the CLL and the amount of time it takes for the number of lymphocytes to double.

Treatment

Because the long-term prognosis for many patients with CLL is excellent, many patients receive no treatment at all at first. Many patients go for years before developing aggressive disease that requires treatment. Treatment for early stage CLL should be started only when one of the following conditions appears:

  • Symptoms of the disease are growing worse, for example, there is a greater degree of fever, weight loss, night sweats, and so forth.
  • The spleen is enlarging or enlargement of the spleen has become painful.
  • Disease of the lymph nodes has become more severe.
  • The condition of the bone marrow has deteriorated and there is anemia and a marked reduction in the number of blood platelets.
  • There is anemia or reduction in the number of blood platelets for reasons not specifically related to the condition of the bone marrow.
  • The population of lymphocytes is rapidly growing.
  • The patient is experiencing numerous infections caused by bacteria.

Therapy for CLL usually starts with chemotherapy . Depending on the stage of the disease, single or multiple drugs may be given. Drugs commonly prescribed include fludarabine , cladribine , chlorambucil and cyclophosphamide . Studies have also provided evidence that a combination of fludarabine and cyclophosphamide is effective. However, this combination has not yet been evaluated over periods of ten years or more. Another combination now being studied involves fludarabine and mitoxantrone (Novantrone). Yet another involves fludarabine and anthracyclines. Low-dose radiation therapy may be given to the whole body, or it may be used to alleviate the symptoms and discomfort due to an enlarged spleen and lymph nodes. The spleen may be removed in a procedure called a splenectomy .

Bone marrow transplantation (BMT) has produced some positive outcomes in patients with CLL, although it has not been the subject of sufficient systematic study to permit doctors to know how effective it is. In BMT, the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of performing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from another person (donor) whose tissue is either the same or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. To replace the destroyed marrow, healthy marrow from the donor is given to the patient through a needle in the vein.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is then destroyed with high-dose chemotherapy and radiation therapy. Following that, the patient's own frozen marrow is thawed and given back to the patient through a needle in the vein. The use of this mode of bone marrow transplant for the treatment of CLL is currently being investigated in clinical trials .

Allogeneic BMT has been successfully used with younger patients with CLL who have not responded positively to chemotherapy. Autologous BMT has produced some positive results in older CLL patients. However, BMT is generally not considered an option in treating most patients with CLL because they are too old to be considered good candidates for the procedure.

Other CLL therapies that are being investigated include monoclonal antibody-targeted therapy and inter-ferons . Monoclonal antibodies (MoAbs) are laboratory-manufactured chemicals that closely resemble parts of the body's natural immune system. Studies of MoAbs-targeted therapies have shown some positive results in CLL, although definitive studies have not been performed at the time of this writing in 2001. Interferon is a chemical normally made in the cells of the body. It helps protect the body against viruses and also seems to have some effect against certain cancers. The interferon used as medicine is a laboratory-manufactured copy of the interferon produced by the body. As of this writing in 2001, interferon therapy has produced some response in CLL patients. However, interferon therapy has not as yet been shown to be associated with prolongation of remission.

Radiation therapy is very effective for approximately one in three of those CLL patients for whom it is considered appropriate.

Because leukemia cells can spread to all the organs via the blood stream and the lymph vessels, surgery is not considered an option for treating leukemias.

Treatment of CLL and its complications

During therapy for CLL, complications frequently appear. Many patients develop infectious illnesses. Sometimes, two or more infectious diseases attack a patient at the same time. These infections should be treated with great care. Most people whose death has been directly attributed to CLL have actually died from bacterial infections. The patient should be involved in identifying symptoms of infection and reporting these to the doctor without delay. Doing so may save the patient's life.

Many patients develop anemia, which is treated with the drug prednisone. Patients who do not respond to prednisone therapy may have their spleen removed and may receive therapy with immunoglobulin, a component of the blood.

Treatment after transformation of CLL

Between three and ten out of every hundred patients with CLL experiences transformation of the disease into large-cell lymphoma (LCL). When this happens it is called Richter's transformation. Its occurrence is often marked by fever, weight loss, and night sweats. Treatments for LCL are being studied, although outcomes have not been very good. Very infrequently, CLL may transform into another disease, called prolymphocytic leukemia. Attempts to develop adequate therapies for this disease are ongoing.

Prognosis

For many CLL patients, the prognosis is excellent. Using the Binet and Rai staging systems, patients at low risk usually survive more than ten years. Patients at intermediate risk usually survive about six years. Patients at high risk usually survive about two years. The average patient survives approximately nine years following diagnosis. Factors with important implications for prognosis that are not included in the Binet or Rai systems are the pattern at which bone marrow is being affected by the CLL and the amount of time it takes for the number of lymphocytes in the blood to double. It is uncertain whether BMT may prolong the lifespan of CLL patients. Many of the chemotherapy agents used to treat disease do effectively control the leukemia and its effects but, as yet, the more established chemotherapy agents have not been shown to increase the life span of patients.

Coping with cancer treatment

Since many CLL patients die from infection, it is essential that patient be very alert to the signs of infection. If patients perform this role and seek medical attention as soon as symptoms of infection appear, then treatment can be started early. This may save a life.

It is very difficult for some patients to be not only informed that they have leukemia but then to also be told that they do not need treatment. This may be very confusing, unless the patient realizes that treatment may be necessary at some future time and that starting therapies too soon may be counterproductive.

Because nutritional alteration, weight loss, and psychosocial problems may accompany CLL, it may be prudent for patients to consult with a registered dietitian.

Cancer patients need supportive care to help them come through the treatment period with physical and emotional strength in tact. Many patients experience feelings of depression , anxiety, and fatigue, and many experience nausea and vomiting during treatment. Studies have shown that these can be managed effectively if discussed with the attending physician.

Prevention

Although some cancers are related to known risk factors, such as smoking, in leukemias, there are no known risk factors. Therefore, at the present time, there is no way known to prevent the leukemias from developing. Everyone should undergo periodic medical checkups.

Resources

BOOKS

Braunwald, Eugene, et al. Harrison's Principles of Internal Medicine 15th ed. New York: McGraw-Hill, 2001.

deWitt, Susan C. Essentials of Medical-Surgical Nursing 4th ed. Philadelphia: W. B. Saunders, 1998.

Herfindal, Eric T., Dick R. Gourley. Textbook of Therapeutics: Drug and Disease Management, 7th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.

Humes, H. David, et al. Kelley's Textbook of Internal Medicine 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.

Pazdur, Richard, et al. Cancer Management: A Multidisciplinary Approach: Medical, Surgical, & Radiation Oncology 4th ed. Melville, NY: PRR, 2000.

Souhami, Robert, Jeffrey Tobias. Cancer and Its Management 3rd ed. London: Blackwell Science, 1998.

PERIODICALS

Mauro, F. R., et al. "Clinical characteristics and outcome of young chronic lymphocytic leukemia patients: A single institution study of 204 cases." Blood 1999; 94: 448-454.

ORGANIZATIONS

The National Cancer Institute publishes useful texts available through the internet or by mail, and answers questions by telephone. Some titles include: What You Need to Know about Leukemia, and PDQ -Treatment -Patients: Chronic Lymphocytic Leukemia. Call 1-800-4CANCER or visit on the Internet at <www.nci.nih.gov/>.

The American Cancer Society publishes useful texts, such asAdult Chronic Leukemia -Overview, Leukemia -Adult Chronic: Treatment, Leukemia -Adult Chronic: Detection and Symptoms, Leukemia: Adult Chronic FAQ [Frequently Asked Questions], and Leukemia -Adult Chronic: Prevention & Risk. Call 1-800-ACS-2345 or on the Internet at <www.cancer.org/>

The Leukemia & Lymphoma Society (Formerly Leukemia Society of America) publishes useful texts available through the Internet or by mail, including Chronic Lymphocytic Leukemia (CLL), Making Intelligent Choices About Therapy, Understanding Blood Counts, Patient Aid Program, Family Support Group, and Information Resource Center. Call 1-800-955-4572 or visit on the Internet at <www.leukemia-lymphoma.org/>.

National Coalition for Cancer Survivorship. 1010 Wayne Avenue, 7th Floor, Silver Spring, MD 20910-5600. Telephone: (301) 650-9127 and (877) NCCS-YES [877-622-7937). Web site: <www.cansearch.org>.

Lata Cherath, Ph.D.

Bob Kirsch

KEY TERMS

Antibodies

Proteins made by the B lymphocytes in response to the presence of infectious agents, such as bacteria or viruses, in the body.

Biopsy

The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy

Treatment with drugs that act against cancer.

Chromosome

Part of the cell that carries genetic material.

Cytokines

Chemicals made by the cells that act on other cells to stimulate or inhibit their function. Cytokines that stimulate growth are called "growth factors."

Immunotherapy

Treatment of cancer by stimulating the body's immune defense system.

Maturation

The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy

Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Remission

A disappearance of a disease as a result of treatment. Complete remission means that all disease is gone. Partial remission means that the disease is significantly improved by treatment, but residual traces of the disease are still present.

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Leukemias, Chronic

Leukemias, chronic

Definition

Chronic leukemia is a disease in which abnormal, cancerous white blood cells are made in the bone marrow. Depending on the type of white blood cell that is involved, chronic leukemia can be classified as chronic lymphocytic leukemia or chronic myeloid leukemia.

Description

Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called blasts or stem cells, which mature into different types of blood cells. Unlike acute leukemias , in which the process of maturation of the blast cells is interrupted, in chronic leukemias, the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.

Bone marrow produces different types of cells: red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and platelets, which play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: the granulocytes, monocytes, and the lymphocytes.

The granulocytes, as their name suggests, contain granules (particles). These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria.

Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. There are two main types of lymphocytes: T lymphocytes and B lymphocytes. They have different functions within the immune system. The B cells protect the body by making antibodies, which are proteins that can attach to the surfaces of bacteria and viruses. This attachment sends signals to many other cell types to come and destroy the antibody-coated organism. The T cell protects the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. The T cells can recognize these proteins and produce certain chemicals (cytokines) that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

Chronic leukemias develop very gradually. The abnormal lymphocytes multiply slowly, but in a poorly regulated manner. They live much longer and thus their numbers build up in the body. The two types of chronic leukemias can be easily distinguished under the microscope. Chronic lymphocytic leukemia (CLL) involves the T or B lymphocytes. B cell abnormalities are more common than T cell abnormalities. T cells are affected in only 5 percent of the patients. The T and B lymphocytes can be differentiated from the other types of white blood cells based on their size and by the absence of granules inside them. In chronic myelogenous leukemia (CML), the cells that are affected are the granulocytes.

Chronic lymphocytic leukemia (CLL) often has no symptoms at first and may remain undetected for a long time. Chronic myelogenous leukemia (CML), by contrast, may progress to a more acute form.

Demographics

Chronic leukemias account for 1.2 percent of all cancers. Because leukemia is the most common form of childhood cancer, it is often regarded as a disease of childhood. However, leukemias affect nine times as many adults as children. In chronic lymphoid leukemia, 90 percent of the cases are seen in people who are 50 years or older, with the average age at diagnosis being 65. The incidence of the disease increases with age. It is almost never seen in children. Chronic myeloid leukemias are generally seen in people in their mid-40s. In addition, it accounts for about 4 percent of childhood leukemia cases.

Causes and symptoms

Leukemia strikes both sexes and all ages. Although the cause is unknown, chronic leukemia is linked to genetic abnormalities and environmental factors. For example, exposure to ionizing radiation and to certain organic chemicals, such as benzene, is believed to increase the risks for getting leukemia. Chronic leukemia occurs in some people who are infected with two human retroviruses (HTLV-I and HTLV-II). An abnormal chromosome known as the Philadelphia chromosome is seen in 90 percent of those with CML. The incidence of chronic leukemia is slightly higher among men than women.

The symptoms of chronic leukemia are generally vague and non-specific. In chronic lymphoid leukemia (CLL), a patient may experience all or some of the following symptoms:

  • swollen lymph nodes
  • an enlarged spleen, which could make the patient complain of abdominal fullness
  • chronic fatigue
  • a general feeling of ill-health
  • fever of unknown origin
  • night sweats
  • weight loss that is not due to dieting or exercise
  • frequent bacterial or viral infections

In the early stages of chronic myeloid leukemia (CML), the symptoms are more or less similar to CLL. In the later stages of the disease, the patient may experience the following symptoms:

  • non-specific bone pain
  • bleeding problems
  • mucus membrane irritation
  • frequent infections
  • a pale color due to a low red blood cell count (anemia)
  • swollen lymph glands
  • fever
  • night sweats

Diagnosis

There are no screening tests available for chronic leukemias. The detection of these diseases may occur by chance during a routine physical examination.

If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, an enlarged liver or spleen, bruises , or pinpoint red rashes all over the body are some of the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia; however, the diagnosis has to be confirmed by more specific tests.

The doctor may perform a bone marrow biopsy to confirm the diagnosis of leukemia. During the bone marrow biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hip-bone. These samples are sent to the laboratory for examination. In addition to diagnosis, bone marrow biopsy is also done during the treatment phase of the disease to see if the leukemia is responding to therapy.

Standard imaging tests such as x-rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other organs of the body, such as the bones, chest, kidneys, abdomen, or brain.

Treatment

The treatment depends on the specific type of chronic leukemia and its stage. In general, chemotherapy is the standard approach to both CLL and CML. Radiation therapy is occasionally used. Because leukemia cells can spread to all the organs via the blood stream and the lymph vessels, surgery is not considered an option for treating leukemias.

Bone marrow transplantation (BMT) is in the early 2000s becoming the treatment of choice for CML because it has the possibility of curing the illness. BMT is generally not considered an option in treating CLL because CLL primarily affects older people, who are not considered to be good candidates for the procedure.

In BMT, the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from another person (donor) whose tissue is either the same or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. To replace the destroyed marrow, healthy marrow from the donor is given to the patient through a needle in the vein.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is then destroyed with high dose chemotherapy and radiation therapy. Following that, the patient's own marrow that was frozen is thawed and given back to the patient through a needle in the vein. This mode of bone marrow transplant is as of the early 2000s being investigated in clinical trials.

In chronic lymphoid leukemia (CLL), chemotherapy is generally the treatment of choice. Depending on the stage of the disease, single or multiple drugs may be given. Drugs commonly prescribed are steroids, chlorambucil, fludarabine, and cladribine. Low dose radiation therapy may be given to the whole body, or it may be used to alleviate the symptoms and discomfort due to an enlarged spleen and lymph nodes. The spleen may be removed in a procedure called a splenectomy.

In chronic myeloid leukemia (CML), the treatment of choice is bone marrow transplantation. During the slow progress (chronic phase) of the disease, chemotherapy may be given to try to improve the cell counts. Radiation therapy, which involves the use of x rays or other high-energy rays to kill cancer cells and shrink tumors, may be used in some cases to reduce the discomfort and pain due to an enlarged spleen. For chronic leukemias, the source of radiation is usually outside the body (external radiation therapy). If the leukemic cells have spread to the brain, radiation therapy can be directed at the brain. As the disease progresses, the spleen may be removed in an attempt to try to control the pain and to improve the blood counts.

In the acute phase of CML, aggressive chemotherapy is given. Combination chemotherapy, in which multiple drugs are used, is more efficient than using a single drug for the treatment. The drugs may either be administered intravenously (through a vein) in the arm or by mouth in the form of pills. If the cancer cells have invaded the central nervous system (CNS), chemotherapeutic drugs may be put into the fluid that surrounds the brain through a needle in the brain or back. This is known as intrathecal chemotherapy.

Biological therapy or immunotherapy is a mode of treatment in which the body's own immune system is harnessed to fight the cancer. Substances that are routinely made by the immune system (such as growth factors, hormones, and disease-fighting proteins) are either synthetically made in a laboratory, or their effectiveness is boosted and they are then put back into the patient's body. This treatment mode in the early 2000s is also being investigated in clinical trials all over the United States at major cancer centers.

Prognosis

The prognosis for leukemia depends on the patient's age and general health. According to statistics, in chronic lymphoid leukemia, the overall survival for all stages of the disease is nine years. Most of the deaths in people with CLL are due to infections or other illnesses that occur as a result of the leukemia.

In CML, if bone marrow transplantation is performed within one to three years of diagnosis, 50 to 60 percent of the patients survive three years or more. If the disease progresses to the acute phase, the prognosis is poor. Less than 20 percent of these patients go into remission.

KEY TERMS

Antibody A special protein made by the body's immune system as a defense against foreign material (bacteria, viruses, etc.) that enters the body. It is uniquely designed to attack and neutralize the specific antigen that triggered the immune response.

Biopsy The surgical removal and microscopic examination of living tissue for diagnostic purposes or to follow the course of a disease. Most commonly the term refers to the collection and analysis of tissue from a suspected tumor to establish malignancy.

Chemotherapy Any treatment of an illness with chemical agents. The term is usually used to describe the treatment of cancer with drugs that inhibit cancer growth or destroy cancer cells.

Computed tomography (CT) An imaging technique in which cross-sectional x rays of the body are compiled to create a three-dimensional image of the body's internal structures; also called computed axial tomography.

Cytokines Chemicals made by the cells that act on other cells to stimulate or inhibit their function. They are important controllers of immune functions.

Immunotherapy A mode of cancer treatment in which the immune system is stimulated to fight the cancer.

Lumbar puncture A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw spinal fluid for testing. Also known as a spinal tap.

Magnetic resonance imaging (MRI) An imaging technique that uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct detailed images of internal body structures and organs, including the brain.

Maturation The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy A cancer treatment that uses high-energy rays or particles to kill or weaken cancer cells. Radiation may be delivered externally or internally via surgically implanted pellets. Also called radiotherapy.

Remission A disappearance of a disease and its symptoms. Complete remission means that all disease is gone. Partial remission means that the disease is significantly improved, but residual traces of the disease are still present. A remission may be due to treatment or may be spontaneous.

Prevention

Most cancers can be prevented by changes in lifestyle or diet, which will reduce the risk factors. However, in leukemias, there were as of 2004 no known risk factors. Therefore, as of 2004, there was no way known to prevent the leukemias from developing. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation, the organic liquid benzene, or people who have a history of other cancers of the lymphoid system (Hodgkin's lymphoma) should undergo periodic medical checkups.

Parental concerns

Parents of a child with leukemia must balance their own fears for their child's health with the child's fears and worries. Also, given the large financial burden leukemia treatment entails, parents will want to make sure they are aware of what and what is not covered by their insurance. Parents can find a variety of sources, written and online, that will help them deal with the new circumstances of themselves and their family .

Resources

BOOKS

Cheson, Bruce D. "Chronic Lymphoid Leukemias." In Clinical Oncology. Edited by Martin D. Abeloff. London: Churchill Livingstone, 2000.

. "Chronic Myeloid Leukemias." In Clinical Oncology. Edited by Martin D. Abeloff. London: Churchill Livingstone, 2000.

Tubergen, David G., and Archie Bleyer. "The Leukemias." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Rd., NE, Atlanta, GA 303294251. Web site: <www.cancer.org>.

Cancer Research Institute. 681 Fifth Ave., New York, NY 10022. Web site: <www.cancerresearch.org>.

Leukemia Society of America Inc. 600 Third Ave., New York, NY 10016. Web site: <www.leukemia.org>.

National Cancer Institute. Building 31, Room 10A31, 31 Center Drive, MSC 2580, Bethesda, MD 208922580. Web site: <www.nci.nih.gov>.

Lata Cherath, PhD Rosalyn Carson-DeWitt, MD

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Leukemias, Chronic

Leukemias, Chronic

Definition

Chronic leukemia is a disease in which too many white blood cells are made in the bone marrow. Depending on the type of white blood cell that is involved, chronic leukemia can be classified as chronic lymphocytic leukemia or chronic myeloid leukemia.

Description

Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called "blasts" or "stem cells" that mature into different types of blood cells. Unlike acute leukemias, in which the process of maturation of the blast cells is interrupted, in chronic leukemias, the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.

The different types of cells that are produced in the bone marrow are red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and platelets, which play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: the granulocytes, monocytes, and the lymphocytes.

The granulocytes, as their name suggests, have granules (particles) inside them. These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria.

Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. There are two main types of lymphocytes: T lymphocytes and B lymphocytes. They have different functions within the immune system. The B cells protect the body by making "antibodies." Antibodies are proteins that can attach to the surfaces of bacteria and viruses. This attachment sends signals to many other cell types to come and destroy the antibody-coated organism. The T cell protects the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. The T cells can recognize these proteins and produce certain chemicals (cytokines) that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

Chronic leukemias develop very gradually. The abnormal lymphocytes multiply slowly, but in a poorly regulated manner. They live much longer and thus their numbers build up in the body. The two types of chronic leukemias can be easily distinguished under the microscope. Chronic lymphocytic leukemia (CLL) involves the T or B lymphocytes. B cell abnormalities are more common than T cell abnormalities. T cells are affected in only 5% of the patients. The T and B lymphocytes can be differentiated from the other types of white blood cells based on their size and by the absence of granules inside them. In chronic myelogenous leukemia (CML), the cells that are affected are the granulocytes.

Chronic lymphocytic leukemia (CLL) often has no symptoms at first and may remain undetected for a long time. Chronic myelogenous leukemia (CML), on the other hand, may progress to a more acute form.

Chronic leukemias account for 1.2% of all cancers. Because leukemia is the most common form of childhood cancer, it is often regarded as a disease of childhood. However, leukemias affect nine times as many adults as children. In chronic lymphoid leukemia, 90% of the cases are seen in people who are 50 years or older, with the average age at diagnosis being 65. The incidence of the disease increases with age. It is almost never seen in children. Chronic myeloid leukemias are generally seen in people in their mid-40s. It accounts for about 4% of childhood leukemia cases. According to the estimates of the American Cancer Society (ACS), approximately 29,000 new cases of leukemia will be diagnosed in 1998.

Causes and symptoms

Leukemia strikes both sexes and all ages. Although the cause is unknown, chronic leukemia is linked to genetic abnormalities and environmental factors. For example, exposure to ionizing radiation and to certain organic chemicals, such as benzene, is believed to increase the risks for getting leukemia. Chronic leukemia occurs in some people who are infected with two human retroviruses (HTLV-I and HTLV-II). An abnormal chromosome known as the Philadelphia chromosome is seen in 90% of those with CML. The incidence of chronic leukemia is slightly higher among men than women.

The symptoms of chronic leukemia are generally vague and non-specific. In chronic lymphoid leukemia (CLL), a patient may experience all or some of the following symptoms:

  • swollen lymph nodes
  • an enlarged spleen, which could make the patient complain of abdominal fullness
  • chronic fatigue
  • a general feeling of ill-health
  • fever of unknown origin
  • night sweats
  • weight loss that is not due to dieting or exercise
  • frequent bacterial or viral infections

In the early stages of chronic myeloid leukemia (CML), the symptoms are more or less similar to CLL. In the later stages of the disease, the patient may experience these symptoms:

  • non-specific bone pain
  • bleeding problems
  • mucus membrane irritation
  • frequent infections
  • a pale color due to a low red blood cell count (anemia)
  • swollen lymph glands
  • fever
  • night sweats

Diagnosis

There are no screening tests available for chronic leukemias. The detection of these diseases may occur by chance during a routine physical examination.

If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, an enlarged liver or spleen, bruises, or pinpoint red rashes all over the body are some of the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia; however, the diagnosis has to be confirmed by more specific tests.

The doctor may perform a bone marrow biopsy to confirm the diagnosis of leukemia. During the bone marrow biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hipbone. These samples are sent to the laboratory for examination. In addition to diagnosis, bone marrow biopsy is also done during the treatment phase of the disease to see if the leukemia is responding to therapy.

Standard imaging tests such as x rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other organs of the body, such as the bones, chest, kidneys, abdomen, or brain.

Treatment

The treatment depends on the specific type of chronic leukemia and its stage. In general, chemotherapy is the standard approach to both CLL and CML. Radiation therapy is occasionally used. Because leukemia cells can spread to all the organs via the blood stream and the lymph vessels, surgery is not considered an option for treating leukemias.

Bone marrow transplantation (BMT) is becoming the treatment of choice for CML because it has the possibility of curing the illness. BMT is generally not considered an option in treating CLL because CLL primarily affects older people, who are not considered to be good candidates for the procedure.

In BMT, the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from another person (donor) whose tissue is either the same or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. To replace the destroyed marrow, healthy marrow from the donor is given to the patient through a needle in the vein.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is then destroyed with high dose chemotherapy and radiation therapy. Following that, the patient's own marrow that was frozen is thawed and given back to the patient through a needle in the vein. This mode of bone marrow transplant is currently being investigated in clinical trials.

In chronic lymphoid leukemia (CLL), chemotherapy is generally the treatment of choice. Depending on the stage of the disease, single or multiple drugs may be given. Drugs commonly prescribed include steroids, chlorambucil, fludarabine, and cladribine. Low dose radiation therapy may be given to the whole body, or it may be used to alleviate the symptoms and discomfort due to an enlarged spleen and lymph nodes. The spleen may be removed in a procedure called a splenectomy.

In chronic myeloid leukemia (CML), the treatment of choice is bone marrow transplantation. During the slow progress (chronic phase) of the disease, chemotherapy may be given to try to improve the cell counts. Radiation therapy, which involves the use of x rays or other high-energy rays to kill cancer cells and shrink tumors, may be used in some cases to reduce the discomfort and pain due to an enlarged spleen. For chronic leukemias, the source of radiation is usually outside the body (external radiation therapy). If the leukemic cells have spread to the brain, radiation therapy can be directed at the brain. As the disease progresses, the spleen may be removed in an attempt to try to control the pain and to improve the blood counts.

In the acute phase of CML, aggressive chemotherapy is given. Combination chemotherapy, in which multiple drugs are used, is more efficient than using a single drug for the treatment. The drugs may either be administered intravenously through a vein in the arm or by mouth in the form of pills. If the cancer cells have invaded the central nervous system (CNS), chemotherapeutic drugs may be put into the fluid that surrounds the brain through a needle in the brain or back. This is known as intrathecal chemotherapy.

Biological therapy or immunotherapy is a mode of treatment in which the body's own immune system is harnessed to fight the cancer. Substances that are routinely made by the immune system (such as growth factors, hormones, and disease-fighting proteins) are either synthetically made in a laboratory, or their effectiveness is boosted and they are then put back into the patient's body. This treatment mode is also being investigated in clinical trials all over the country at major cancer centers.

Prognosis

The prognosis for leukemia depends on the patient's age and general health. According to statistics, in chronic lymphoid leukemia, the overall survival for all stages of the disease is nine years. Most of the deaths in people with CLL are due to infections or other illnesses that occur as a result of the leukemia.

In CML, if bone marrow transplantation is performed within one to three years of diagnosis, 50-60% of the patients survive three years or more. If the disease progresses to the acute phase, the prognosis is poor. Less than 20% of these patients go into remission.

KEY TERMS

Antibodies Proteins made by the B lymphocytes in response to the presence of infectious agents, such as bacteria or viruses, in the body.

Biopsy The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy Treatment with drugs that act against cancer.

Computerized tomography (CT) scan A series of x rays put together by a computer in order to form detailed pictures of areas inside the body.

Cytokines Chemicals made by the cells that act on other cells to stimulate or inhibit their function. Cytokines that stimulate growth are called "growth factors."

Immunotherapy Treatment of cancer by stimulating the body's immune defense system.

Lumbar puncture A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw some spinal fluid for testing. Also known as a "spinal tap."

Magnetic resonance imaging (MRI) A medical procedure using a magnet linked to a computer to picture areas inside the body.

Maturation The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Remission A disappearance of a disease as a result of treatment. Complete remission means that all disease is gone. Partial remission means that the disease is significantly improved by treatment, but residual traces of the disease are still present.

Prevention

Most cancers can be prevented by changes in lifestyle or diet, which will reduce the risk factors. However, in leukemias, there are no known risk factors. Therefore, at the present time, there is no way known to prevent the leukemias from developing. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation, the organic liquid benzene, or people who have a history of other cancers of the lymphoid system (Hodgkin's lymphoma) should undergo periodic medical checkups.

Resources

ORGANIZATIONS

American Cancer Society. 1599 Clifton Rd., NE, Atlanta, GA 30329-4251. (800) 227-2345. http://www.cancer.org.

Cancer Research Institute. 681 Fifth Ave., New York, N.Y. 10022. (800) 992-2623. http://www.cancerresearch.org.

Leukemia Society of America, Inc. 600 Third Ave., New York, NY 10016. (800) 955 4572. http://www.leukemia.org.

National Cancer Institute. Building 31, Room 10A31, 31 Center Drive, MSC 2580, Bethesda, MD 20892-2580. (800) 422-6237. http://www.nci.nih.gov.

Oncolink. University of Pennsylvania Cancer Center. http://cancer.med.upenn.edu.

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Chronic Leukemia

Chronic leukemia

Definition

A slowly progressing cancer that starts in blood-forming cells of the bone marrow. Leukemias are the result of an abnormal development of leukocytes (white blood cells) and their precursors. Leukemia cells look different than normal cells and do not function properly.

Description

There are four main types of leukemia, which can be further divided into subtypes. When classifying the type of leukemia, the first steps are to determine whether the cancer is lymphocytic or myelogenous (cancer can occur in either the lymphoid or myeloid white blood cells) and whether it is acute or chronic (rapidly or slowly progressing).

Chronic leukemia cells live much longer than normal white blood cells, resulting in an accumulation of too many mature granulocytes or lymphocytes. Chronic leukemia progresses slowly but can develop into an acute form. Major types include chronic lymphocytic leukemia (CLL) and chronic myelocytic leukemia (CML).

Kate Kretschmann

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Chronic Leukemia

Chronic leukemia

Definition

A slowly progressing cancer that starts in blood-forming cells of the bone marrow. Leukemias are the result of an abnormal development of leukocytes (white blood cells) and their precursors. Leukemia cells look different than normal cells and do not function properly.

Description

There are four main types of leukemia, which can be further divided into subtypes. When classifying the type of leukemia, the first steps are to determine whether the cancer is lymphocytic or myelogenous (cancer can occur in either the lymphoid or myeloid white blood cells) and whether it is acute or chronic (rapidly or slowly progressing).

Chronic leukemia cells live much longer than normal white blood cells, resulting in an accumulation of too many mature granulocytes or lymphocytes. Chronic leukemia progresses slowly but can develop into an acute form. Major types include chronic lymphocytic leukemia (CLL) and chronic myelocytic leukemia (CML).

Kate Kretschmann

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Leukemias, Chronic

Leukemias, Chronic

Definition

Chronic leukemia is a type of cancer in which excessive quantities of abnormal white blood cells are produced, usually slowly, often over a period of years.

Description

Medical science classifies chronic leukemia by the type of white blood cell that undergoes mutation. The most common of these are:

  • Chronic lymphocytic leukemia (CLL), in which mature-appearing white blood cells called lymphocytes are produced.
  • Chronic myeloid (or myelogenous) leukemia (CML), also known as chronic granulocytic leukemia (CGL), is the result of uncontrolled proliferation of white blood cells called granulocytes.

Chronic leukemias are much less rapid-growing than acute leukemia, and affect adults far more often than children. In fact, nearly all the people who develop CLL are over 50 years of age. CML is also a disease primarily of middle-aged to elderly people, but 3% of all childhood leukemias are classified as CML, and the average age for developing CML is between ages 10 and 12.

The cells that make up blood are produced in the bone marrow and the lymph system. The bone marrow is the spongy tissue found in the large bones of the body. The lymph system includes the spleen (an organ in the upper abdomen), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat). The lymph vessels (tiny tubes that branch like blood vessels into all parts of the body) and lymph nodes (small pea-shaped organs that are found along the network of lymph vessels) are also part of the lymph system. The lymph itself is a milky fluid that contains cells. Clusters of lymph nodes are found in the neck, underarm, pelvis, abdomen, and chest.

The cells found in the blood are the red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and the platelets, which play an important role in the clotting of the blood. The white blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes.

The granulocytes have particles (granules) inside them that contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. The two primary types of lymphocytes, T lymphocytes and B lymphocytes, have different functions within the immune system. The B cells protect the body by making antibodies, which are proteins that can attach to the surfaces of bacteria and viruses. This attachment sends signals to many other cell types to destroy the antibody-coated organism. The T cells protect the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. The T cells recognize these proteins and make certain chemicals that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

The bone marrow makes stem cells, which are the precursors of the different blood cells. Stem cells mature into RBCs, WBCs, or platelets. In chronic leukemias, blood cells suddenly begin to proliferate rapidly and begin to accumulate in various organs and tissues, thereby affecting their normal function. This uncontrolled proliferation of the immature cells in the bone marrow affects the production of the normal red blood cells and platelets as well.

Different types of white blood cells are involved in chronic lymphocytic leukemia and chronic myeloid leukemia. Although some blasts, or immature cells (the hallmark of acute leukemia), are also present in chronic leukemia, it is the T or B lymphocytes that gradually mutate and become cancerous. The scenario is similar for chronic myelogenous leukemia, also known as chronic granulocytic leukemia (CGL), which occurs when unusually large numbers of granulocytes begin to appear in the bloodstream.

Leukemias account for 2% of all cancers. According to the estimates of the American Cancer Society (ACS), approximately 29,000 new cases of leukemia are diagnosed each year in the United States. Of these, 27,000 will be diagnosed in adults, 2000 in children. Leukemia is the most common form of childhood cancer, and it is often regarded as a disease of childhood However, leukemias, especially chronic leukemia, affect far more adults than children. Half of all leukemia cases occur in people who are 60 years of age or older, and the overwhelming majority of chronic leukemias occur in adults. The incidence of both acute and chronic leukemias is about the same.

Causes and symptoms

Leukemia strikes both sexes and all ages. The human T-cell leukemia virus (HTLV-I), a virus with similarities to the human immunovirus (HIV), is believed to be the causative agent for some kinds of leukemias, but this has not yet been proven. To date, the cause of most leukemias is not known. Lymphoid leukemias are more common among Caucasians than among African-Americans, while myeloid leukemias affects both races equally. The incidence of leukemia is slightly higher among men than women. People with Jewish ancestry have a higher likelihood of getting leukemia. A higher incidence of leukemia has also been observed among persons with Down syndrome and some other genetic abnormalities. Patients with chronic myeloid leukemia often show a chromosome abnormality called the Philadelphia chromosome that occurs when one chromosome attaches to another.

Exposure to ionizing radiation, such as occurred in Japan after the atomic bomb explosions, has been shown to increase the risk of getting leukemia. Electromagnetic fields are suspected of being a possible cause, as are certain organic chemicals such as benzene. Having a history of diseases that damage the bone marrow, such as aplastic anemia, or a history of cancers of the lymphatic system puts people at a high risk for developing leukemias. Similarly, the use of anticancer medications, immunosuppressants, and the antibiotic chloramphenicol are also considered risk factors for developing leukemias.

In 2003, the Institute of Medicine (IOM) released a report based upon scientific studies that found "sufficient evidence of an association" between CLL and exposure to herbicides during the Vietnam War. This report came from a Veterans Administration (VA) request to IOM to explore some similarities between CLL and non-Hodgkin's lymphoma. Non-Hodgkin's lymphoma has already been linked to Agent Orange exposure and is recognized by VA as a presumptive condition.

The symptoms of chronic leukemia are generally vague and non-specific, and are frequently overlooked until they are noticed on routine physical examination, especially when a routine blood test such as a complete blood count (CBC) is performed. A CBC may show unusually large numbers of a certain type of lymphocyte in the blood. Chronic leukemias may go for years without manifesting any symptoms at all, but also can develop symptoms similar to acute leukemias. Chronic myeloid leukemia, in particular, has two phases, a chronic one that can last for several years, and a malignant phase in which immature granulocytes are suddenly generated in huge numbers, producing similar symptoms to acute leukemia. In such cases, a patient may experience all or some of the following symptoms:

  • weakness or chronic fatigue
  • fever of unknown origin, chills, and flu-like symptoms
  • unexplained weight loss
  • frequent bacterial or viral infections
  • viscous (sticky) blood (which slows down the supply to various organs)
  • headache
  • non-specific bone pain
  • easy bruising
  • bleeding from gums or nose
  • blood in urine or stools
  • swollen and tender lymph nodes and/or spleen
  • abdominal fullness
  • night sweats
  • petechiae, or tiny red spots under the skin
  • priapism, or persistent, painful erection of the penis
  • rarely, sores in the eyes or on the skin

Diagnosis

As noted, there are often no symptoms present for chronic leukemia, and there are no screening tests available. If the physician has reason to suspect leukemia, a very thorough physical examination will be conducted to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, enlarged liver or spleen, bruises, or pinpoint red rashes all over the body are some of the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count, which gives the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. However, the diagnosis has to be confirmed by more specific tests.

The physician may perform a bone marrow biopsy, during which a small piece of bone and marrow is removed, generally taken from hipbone. A spinal tap (lumbar puncture) is another procedure that may be ordered. In this procedure, a small needle is inserted into the spinal cavity in the lower back to withdraw some cerebrospinal fluid and to look for leukemic cells.

Standard imaging tests such as x rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other areas of the body, such as the bones, chest, kidneys, abdomen, or brain. A gallium scan, or bone scan, is a test in which a radioactive chemical is injected into the body. The chemical accumulates in the areas of cancer or infection, allowing them to be viewed with a special camera.

Treatment

The need for treatment is assessed according to the degree of enlargement of the liver and spleen, a serious decline in the number of platelets in the blood, and whether or not anemia is present, and if present, how severe. Once begun, the goal of treatment is the same as for acute leukemia: remission, or an arresting of the disease process. There are two phases of treatment for leukemia. The first phase is called induction therapy, in which the main aim is to reduce the number of leukemic cells as much as possible and induce a remission in the patient. Once no leukemic cells are detected in blood tests and bone marrow biopsies, the patient is said to be in remission.

The second phase of treatment is then initiated. This is called continuation, or maintenance therapy, and the aim in this case is to kill any remaining cells and to maintain the remission for as long as possible.

Chemotherapy

Chemotherapy is usually the treatment of choice in leukemia, and is used to relieve symptoms and achieve long-term remission of the disease. Generally, combination chemotherapy, in which multiple drugs are used, is more efficient than using a single drug for the treatment. Some drugs may be administered intravenously (through a vein), while others may be given by mouth in the form of pills. If the cancer cells have invaded the brain, then chemotherapeutic drugs may be put into the fluid that surrounds the brain through a needle in the brain or back. This is known as intrathecal chemotherapy.

Radiation

Radiation therapy, which involves the use of x rays or other high-energy rays to kill cancer cells and shrink tumors, may be used in some cases. For leukemias, the source of radiation is usually outside the body (external radiation therapy). If the leukemic cells have spread to the brain, radiation therapy can be given to the brain.

Bone marrow transplantation

Bone marrow transplantation is a process in which the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from a donor whose tissue is either the same as or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. Healthy marrow from the donor is then administered to the patient through a needle in a vein to replace the destroyed marrow.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is destroyed with high-dose chemotherapy and radiation therapy. The thawed marrow is returned to the patient intravenously. This mode of bone marrow transplant is currently being investigated in clinical trials.

Biological therapy, or immunotherapy, is a mode of treatment in which the body's own immune system is harnessed to fight the cancer. Interferon is a biological therapy that is increasingly being used. Substances that are routinely made by the immune system, such as growth factors, hormones, and disease-fighting proteins, are either synthetically made in a laboratory or their effectiveness is boosted, and they are then put back into the patient's body. This treatment mode is also being investigated in clinical trials all over the country at major cancer centers.

Because leukemia cells can spread to all the organs via the bloodstream and the lymph vessels, surgery is not considered an option for treating leukemias.

Gleevec (imatinib mesylate) tablets were approved by the U.S. Food and Drug Administration (FDA) in May 2003 to treat children with Philadelphia chromosome positive chronic myeloid leukemia (CML)-a rare, life-threatening form of cancer that accounts for 2% of all leukemia in children. This marks the first approval of a new pediatric cancer drug in more than a decade. Gleevec is indicated for children whose disease is in the chronic phase and has recurred after stem cell transplant or for those who are resistant to interferon alpha therapy. The FDA originally approved Gleevec in 2001 for CML in adults. It was approved to treat gastrointestinal stromal tumors in February 2002.

In a 2004 study by the Mayo Clinic in Minnesota, and led by Neil E. Kay, M.D., it was found that a component in green tea helps kill Leukemia cells. Leukemia cells that were studied were taken from 10 patients, with B-cell chronic lymphocytic leukemia (CLL). In this study, it was shown that green tea's component, EGCG, interrupted survival signals, prompting leukemia cells to die in eight of the 10 patient samples studied. This finding is important as it suggests a new, nontoxic treatment for patients with CLL.

Experimental vaccine shows promise

In October 2003, researchers reported in the journal Nature Medicine of their successful tests of a DNA vaccine in mice. In January, further evidence from a trial of the vaccine demonstrated that it could protect at least some of the mice for very long periods of time. The research focused on acute promyeloctyic leukemia (APL) which is currently treated with chemotherapy which cures about 75% of cases. The researchers used a mice model of the disease, exposing one experimental group to the vaccine and another experimental group to the vaccine and chemotherapy. In half the mice receiving the combination of the vaccine and chemotherapy, half the mice lived an additional 300 days-the equivalent of 25 human years. The vaccine uses fragments of a faulty gene found in cancer cells to train the immune system of the animals to recognize and destroy cancerous cells. Despite a major improvement in the survival of APL patients, a cure is still not achieved in all patients. The DNA based vaccine has proven to induce protective immunity. This example of a target therapy in an APL animal model may provide researchers with an alternative therapy, which if translated to humans, will improve quality of life and survival rates for leukemia patients. Any human application is still years away.

Prognosis

Like all cancers, the prognosis for leukemia depends on the patient's age and general health. According to statistics, more than 60% of the patients with leukemia survive for at least a year after diagnosis. More than half the patients diagnosed with chronic lymphocytic leukemia survive for at least five years due to the slowness of the disease process. Eventual death for CLL patients usually is the result of repeated and overwhelming infections. The outlook for chronic myeloid leukemia is generally less optimistic. Overall, average survival time for CML patients from the time of diagnosis is three years. However, 20% of all CML patients survive for at least 10 years, and bone marrow transplantation is improving the outcome.

Health care team roles

In most cases, a diagnosis of leukemia is made in a physician's office, a general medical clinic, or an emergency room by a primary care practitioner. Children and adolescents with leukemia are likely to be diagnosed by their primary care physician, pediatrician, or pediatric nurse practitioner. Oncologists, specialists in the diagnosis and treatment of cancer, are also often involved.

Hematologists, specialists in the diagnosis and treatment of disorders of the blood and the organs that produce blood cells, may be consulted. A pathologist, a specialist in studying tissue and cell samples, may also assist in diagnosis.

Both registered Nurses (RNs) and licensed practical nurses (LPNs) are often the people who deal the most with leukemia patients both in general hospitals, homes, or other health care facilities. Good supportive nursing care and observation are necessary to:

  • Prevent or monitor for infections.
  • Monitor for anemia and bleeding.
  • Assist in treatments such as chemotherapy, radiation, bone-marrow transplantation, or blood transfusions.
  • Monitor vital signs.
  • Provide teaching regarding the prevention of infection, the normal course of leukemia, including fatigue, the signs and symptoms of anemia, and good dental care (both leukemia and chemotherapy can cause sensitivity in the mouth, and vulnerability to infection and bleeding).

Clinical laboratory scientists draw blood samples to monitor the leukemia from the outset, during treatment, and also during remission. Radiologic technologists chest x rays to visualize and monitor parts of the body that may be affected.

Prevention

There is no known way to prevent leukemias. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation or exposure to the toxic liquid benzene, and people with Down syndrome, should undergo periodic medical checkups.

KEY TERMS

Antibodies— Proteins made by the B lymphocytes in response to the presence of infectious agents in the body, such as bacteria or viruses.

Biopsy— The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy— Treatment with anticancer drugs.

Computerized tomography (CT) scan— A series of x rays put together by a computer in order to form detailed pictures of areas inside the body.

Immunotherapy— Treatment of cancer by stimulating the body's immune defense system.

Lumbar puncture— A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw some spinal fluid for testing; also known as a spinal tap.

Magnetic resonance imaging (MRI)— A medical procedure using a magnet linked to a computer to picture areas inside the body.

Maturation— The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy— Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Remission— A disappearance of a disease as a result of treatment. Complete remission means that all disease is gone; partial remission means that the disease is significantly improved by treatment, but residual traces are still present.

Resources

BOOKS

Caligaris-Cappio, Federico, and Riccardo Dalla Favera Chronic Lymphocytic Leukemia New York: Springer, 2005.

Faquet, Guy B. Chronic Lymphocytic Leukemia: Molecular Genetics, Biology, Diagnosis, and Management Totowa, NJ: Humana Press, 2003.

Parker, James N., and Philip M. Parker Chronic Leukemia: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References San Diego: Icon Health Publications, 2004.

Schiller, Gary J. Chronic Leukemias and Lymphomas: Clinical Management Totowa, NJ: Humana Press, 2002.

PERIODICALS

(No author.) "Targeted Approaches May Lead to Better Treatment of Chronic Lymphocytic Leukemia." Blood Weekly (Sept. 4, 2003): 43.

Alexander, Walter. "Changing Drug Use Linked to Better Hematology Responses." Drug Topics (Jan. 26, 2004): HSE-8.

Marin, David, et al. "Survival of Patients with Chronic-Phase Chronic Myeloid Leukaemia on Imatinib After Failure on Interferon Alfa." The Lancet (Aug. 23, 2003): 617.

Millot, Frederic, et al. "Clinical and Biological Features at Diagnosis in 40 Children with Chronic Myeloid Leukemia." Pediatrics (July 2005): 140-143.

Wong, K.K. Jr., and Saswati Chatterjee. "Vaccine Development for Chronic Myelogenous Leukaemia." The Lancet (Feb. 19, 2005): 631.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, Georgia 30329. (800) 227-2345. 〈http://www.cancer.org〉.

Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623. 〈http://www.cancerresearch.org〉.

The Leukemia & Lymphoma Society. 1311 Mamaroneck Ave., White Plains, NY 10605. (914) 949-5213. www.leukemia-lymphoma.org

Leukemia Society of America, Inc. 600 Third Avenue, New York, NY 10016. (800) 955-4572. 〈http://www.leukemia.org〉.

OTHER

Oncolink. University of Pennsylvania Cancer Center. 〈http://cancer.med.upenn.edu〉.

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Leukemias, Chronic

Leukemias, chronic

Definition

Chronic leukemia is a type of cancer in which excessive quantities of abnormal white blood cells are produced, usually slowly, often over a period of years.

Description

Medical science further classifies chronic leukemia by the type of white blood cell that undergoes mutation. The most common of these are:

  • Chronic lymphocytic leukemia (CLL), in which mature-appearing white blood cells called lymphocytes are produced.
  • Chronic myeloid (or myelogenous) leukemia (CML), also known as chronic granulocytic leukemia (CGL), is the result of uncontrolled proliferation of white blood cells called granulocytes.

Chronic leukemias are much less rapid-growing than acute leukemia, and affect adults far more often than children. In fact, nearly all the people who develop CLL are over 50 years of age. CML is also a disease primarily of middle-aged to elderly people, but 3% of all childhood leukemias are classified as CML, and the average age for developing CML is between ages 10 and 12.

The cells that make up blood are produced in the bone marrow and the lymph system. The bone marrow is the spongy tissue found in the large bones of the body. The lymph system includes the spleen (an organ in the upper abdomen), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat). The lymph vessels (tiny tubes that branch like blood vessels into all parts of the body) and lymph nodes (small peashaped organs that are found along the network of lymph vessels) are also part of the lymph system. The lymph itself is a milky fluid that contains cells. Clusters of lymph nodes are found in the neck, underarm, pelvis, abdomen, and chest.

The cells found in the blood are the red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection ; and the platelets, which play an important role in the clotting of the blood. The white blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes.

The granulocytes have particles (granules) inside them that contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria . Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens.

The lymphocytes form the third type of white blood cell. The two primary types of lymphocytes, T lymphocytes and B lymphocytes, have different functions within the immune system . The B cells protect the body by making antibodies, which are proteins that can attach to the surfaces of bacteria and viruses . This attachment sends signals to many other cell types to destroy the anti-body-coated organism. The T cells protect the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. The T cells recognize these proteins and make certain chemicals that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

The bone marrow makes stem cells, which are the precursors of the different blood cells. Stem cells mature into RBCs, WBCs, or platelets. In chronic leukemias, blood cells suddenly begin to proliferate rapidly and begin to accumulate in various organs and tissues, thereby affecting their normal function. This uncontrolled proliferation of the immature cells in the bone marrow affects the production of the normal red blood cells and platelets as well.

Different types of white blood cells are involved in chronic lymphocytic leukemia and chronic myeloid leukemia. Although some blasts, or immature cells (the hallmark of acute leukemia), are also present in chronic leukemia, it is the T or B lymphocytes that gradually mutate and become cancerous. The scenario is similar for chronic myelogenous leukemia, also known as chronic granulocytic leukemia (CGL), which occurs when unusually large numbers of granulocytes begin to appear in the bloodstream.

Leukemias account for 2% of all cancers. According to the estimates of the American Cancer Society (ACS), approximately 29,000 new cases of leukemia are diagnosed each year in the United States. Of these, 27,000 will be diagnosed in adults, 2000 in children. Leukemia is the most common form of childhood cancer, and it is often regarded as a disease of childhood However, leukemias, especially chronic leukemia, affect far more adults than children. Half of all leukemia cases occur in people who are 60 years of age or older, and the over-whelming majority of chronic leukemias occur in adults. The incidence of both acute and chronic leukemias is about the same.

Causes and symptoms

Leukemia strikes both sexes and all ages. The human T-cell leukemia virus (HTLV-I), a virus with similarities to the human immunovirus (HIV), is believed to be the causative agent for some kinds of leukemias, but this has not yet been proven. To date, the cause of most leukemias is not known. Lymphoid leukemias are more common among Caucasians than among African-Americans, while myeloid leukemias affects both races equally. The incidence of leukemia is slightly higher among men than women. People with Jewish ancestry have a higher like-lihood of getting leukemia. A higher incidence of leukemia has also been observed among persons with Down syndrome and some other genetic abnormalities. Patients with chronic myeloid leukemia often show a chromosome abnormality called the Philadelphia chromosome, that occurs when one chromosome attaches to another.

Exposure to ionizing radiation, such as occurred in Japan after the atomic bomb explosions, has been shown to increase the risk of getting leukemia. Electromagnetic fields are suspected of being a possible cause, as are certain organic chemicals such as benzene. Having a history of diseases that damage the bone marrow, such as aplastic anemia, or a history of cancers of the lymphatic system puts people at a high risk for developing leukemias. Similarly, the use of anticancer medications, immunosuppressants, and the antibiotic chloramphenicol are also considered risk factors for developing leukemias.

The symptoms of chronic leukemia are generally vague and non-specific, and are frequently overlooked until they are noticed on routine physical examination , especially when a routine blood test such as a complete blood count (CBC) is performed. A CBC may show unusually large numbers of a certain type of lymphocyte in the blood. Chronic leukemias may go for years without manifesting any symptoms at all, but also can develop symptoms similar to acute leukemias . Chronic myeloid leukemia, in particular, has two phases, a chronic one that can last for several years, and a malignant phase in which immature granulocytes are suddenly generated in huge numbers, producing similar symptoms to acute leukemia. In such cases, a patient may experience all or some of the following symptoms:

  • weakness or chronic fatigue
  • fever of unknown origin, chills, and flu-like symptoms
  • unexplained weight loss
  • frequent bacterial or viral infections
  • viscous (sticky) blood (which slows down the supply to various organs)
  • headache
  • non-specific bone pain
  • easy bruising
  • bleeding from gums or nose
  • blood in urine or stools
  • swollen and tender lymph nodes and/or spleen
  • abdominal fullness
  • night sweats
  • petechiae, or tiny red spots under the skin
  • priapism, or persistent, painful erection of the penis
  • rarely, sores in the eyes or on the skin

Diagnosis

As noted, there are often no symptoms present for chronic leukemia, and there are no screening tests available. If the physician has reason to suspect leukemia, a very thorough physical examination will be conducted to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, enlarged liver or spleen, bruises, or pinpoint red rashes all over the body are some of the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count, which gives the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. However, the diagnosis has to be confirmed by more specific tests.

The physician may perform a bone marrow biopsy, during which a cylindrical piece of bone and marrow is removed, generally taken from hipbone. A spinal tap (lumbar puncture) is another procedure that may be ordered. In this procedure, a small needle is inserted into the spinal cavity in the lower back to withdraw some cerebrospinal fluid and to look for leukemic cells.

Standard imaging tests such as x rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other areas of the body, such as the bones, chest, kidneys , abdomen, or brain . A gallium scan, or bone scan, is a test in which a radioactive chemical is injected into the body. The chemical accumulates in the areas of cancer or infection, allowing them to be viewed with a special camera.

Treatment

The need for treatment is assessed according to the degree of enlargement of the liver and spleen, a serious decline in the number of platelets in the blood, and whether or not anemia is present, and if present, how severe. Once begun, the goal of treatment is the same as for acute leukemia: remission, or an arresting of the disease process. There are two phases of treatment for leukemia. The first phase is called induction therapy, in which the main aim is to reduce the number of leukemic cells as much as possible and induce a remission in the patient. Once no leukemic cells are detected in blood tests and bone marrow biopsies, the patient is said to be in remission.

The second phase of treatment is then initiated. This is called continuation, or maintenance therapy, and the aim in this case is to kill any remaining cells and to maintain the remission for as long as possible.


KEY TERMS


Antibodies —Proteins made by the B lymphocytes in response to the presence of infectious agents in the body, such as bacteria or viruses.

Biopsy —The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy —Treatment with anticancer drugs.

Computerized tomography (CT) scan —A series of x rays put together by a computer in order to form detailed pictures of areas inside the body.

Immunotherapy —Treatment of cancer by stimulating the body's immune defense system.

Lumbar puncture —A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw some spinal fluid for testing; also known as a spinal tap.

Magnetic resonance imaging (MRI) —A medical procedure using a magnet linked to a computer to picture areas inside the body.

Maturation —The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy —Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Remission —A disappearance of a disease as a result of treatment. Complete remission means that all disease is gone; partial remission means that the disease is significantly improved by treatment, but residual traces are still present.


Chemotherapy

Chemotherapy is usually the treatment of choice in leukemia, and is used to relieve symptoms and achieve long-term remission of the disease. Generally, combination chemotherapy, in which multiple drugs are used, is more efficient than using a single drug for the treatment. Some drugs may be administered intravenously (through a vein), while others may be given by mouth in the form of pills. If the cancer cells have invaded the brain, then chemotherapeutic drugs may be put into the fluid that surrounds the brain through a needle in the brain or back. This is known as intrathecal chemotherapy.

Radiation

Radiation therapy, which involves the use of x rays or other high-energy rays to kill cancer cells and shrink tumors, may be used in some cases. For leukemias, the source of radiation is usually outside the body (external radiation therapy). If the leukemic cells have spread to the brain, radiation therapy can be given to the brain.

Bone marrow transplantation

Bone marrow transplantation is a process in which the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from a donor whose tissue is either the same as or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. Healthy marrow from the donor is then administered to the patient through a needle in a vein to replace the destroyed marrow.

In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is destroyed with high-dose chemotherapy and radiation therapy. The thawed marrow is returned to the patient intravenously. This mode of bone marrow transplant is currently being investigated in clinical trials.

Biological therapy, or immunotherapy, is a mode of treatment in which the body's own immune system is harnessed to fight the cancer. Interferon is a biological therapy that is increasingly being used. Substances that are routinely made by the immune system, such as growth factors, hormones, and disease-fighting proteins, are either synthetically made in a laboratory or their effectiveness is boosted, and they are then put back into the patient's body. This treatment mode is also being investigated in clinical trials all over the country at major cancer centers.

Because leukemia cells can spread to all the organs via the bloodstream and the lymph vessels, surgery is not considered an option for treating leukemias.

Prognosis

Like all cancers, the prognosis for leukemia depends on the patient's age and general health. According to statistics, more than 60% of the patients with leukemia survive for at least a year after diagnosis. More than half the patients diagnosed with chronic lymphocytic leukemia survive for at least five years due to the slowness of the disease process. Eventual death for CLL patients usually is the result of repeated and overwhelming infections. The out-look for chronic myeloid leukemia is generally less optimistic. Overall, average survival time for CML patients from the time of diagnosis is three years. However, 20% of all CML patients survive for at least 10 years, and bone marrow transplantation is improving the outcome.

Health care team roles

In most cases, a diagnosis of leukemia is made in a physician's office, a general medical clinic, or an emergency room by a primary care practitioner. Children and adolescents with leukemia are likely to be diagnosed by their primary care physician, pediatrician, or pediatric nurse practitioner. Oncologists, specialists in the diagnosis and treatment of cancer, are also often involved.

Hematologists, specialists in the diagnosis and treatment of disorders of the blood and the organs that produce blood cells, may be consulted. A pathologist, a specialist in studying tissue and cell samples, may also assist in diagnosis.

Both registered Nurses (RNs) and licensed practical nurses (LPNs) are often the people who deal the most with leukemia patients both in general hospitals, homes, or other health care facilities. Good supportive nursing care and observation are necessary to:

  • Prevent or monitor for infections.
  • Monitor for anemia and bleeding.
  • Assist in treatments such as chemotherapy, radiation, bone-marrow transplantation, or blood transfusions.
  • Monitor vital signs.
  • Provide teaching regarding the prevention of infection, the normal course of leukemia, including fatigue, the signs and symptoms of anemia, and good dental care (both leukemia and chemotherapy can cause sensitivity in the mouth, and vulnerability to infection and bleeding).

Clinical laboratory scientists draw blood samples to monitor the leukemia from the outset, during treatment, and also during remission. Radiologic technologists chest x rays to visualize and monitor parts of the body that may be affected.

Prevention

There is no known way to prevent leukemias. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation or exposure to the toxic liquid benzene, and people with Down syndrome, should undergo periodic medical checkups.

Resources

BOOKS

Behrman, Richard E. Nelson Textbook of Pediatrics. Philadephia: W. B. Saunders, 1995.

Berkow, Robert, and Mark H. Beers, eds. Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Murphy, Gerald P. Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment and Recovery. Atlanta, GA: American Cancer Society, 1997.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Road, N.E., Atlanta, Georgia 30329. (800) 227-2345. <http://www.cancer.org>.

Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623. <http://www.cancerresearch.org>.

Leukemia Society of America, Inc. 600 Third Avenue, New York, NY 10016. (800) 955 4572. <http://www.leukemia.org>.

National Cancer Institute. 9000 Rockville Pike, Building 31, Room 10A16, Bethesda, Maryland, 20892. (800) 422-6237. <http://wwwicic.nci.nih.gov>.

Oncolink. University of Pennsylvania Cancer Center. <http://cancer.med.upenn.edu>.

Joan M. Schonbeck

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