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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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"Leukemias, Chronic." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. 18 Oct. 2017 <http://www.encyclopedia.com>.

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"Leukemias, Chronic." Gale Encyclopedia of Medicine, 3rd ed.. . Retrieved October 18, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/leukemias-chronic

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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