Multiple: Brain Tumors
Multiple: Brain Tumors
Brain tumors are abnormal growths of tissue within the brain; about 150 different types have been identified. Brain tumors can be primary or secondary. Primary tumors are tumors that start to grow within the brain. Some are benign, meaning that they are not cancerous. Other primary tumors are malignant, or cancerous. Primary brain tumors are less common than secondary tumors, with most occurring in adults rather than children.
Secondary or metastatic tumors are cancers that start in other organs—most often the breasts, colon, kidneys, lungs, or skin—and then spread to the brain. Most brain tumors are metastatic cancers rather than primary tumors; about a quarter of all adults being treated for cancer in the United States eventually develop metastatic brain tumors. It is rare, however, for primary tumors of the brain to spread to other parts of the body.
Brain tumors vary considerably in their location in the brain, their speed of growth, whether they are benign or malignant, and the specific symptoms they produce. Brain tumors can cause damage by direct destruction of normal brain tissue, by producing inflammation, or by growing so large that they increase pressure inside the skull and interfere with the functioning of other parts of the brain. Primary brain tumors can develop within the brain tissue itself, within the meninges (the membranes that cover and protect the brain and spinal cord), or within the nerves that supply the brain and spinal cord.
In adults, the most common types of brain tumors are gliomas and meningiomas. Gliomas, which account for 78 percent of malignant brain tumors in adults, arise from glial cells, which are the supportive cells in brain tissue that nourish nerve cells and hold them in place. Meningiomas are tumors that arise in the meninges. Ninety percent of mengiomas are benign; however, these tumors can still cause severe complications and death because of their location.
The most widely used system for grading brain tumors was introduced by the World Health Organization (WHO) in 1993. Grading
is based on the tumor's size, its location in the brain, and how fast it grows.
- Grade I. These are slow-growing tumors that may not produce symptoms for many years. They do not usually spread to other parts of the brain and can often be removed completely by surgery.
- Grade II. These tumors are also relatively slow-growing. They can, however, start to grow more rapidly and may spread into other parts of the brain.
- Grade III. Tumors in this category are always malignant and spread rapidly into surrounding tissue. Their cells look different from those in healthy surrounding tissue.
- Grade IV. These tumors invade other tissues very quickly and are difficult to treat. Like Grade III tumors, their cells look very different from healthy brain cells.
About 360,000 persons in the United States are living with a primary brain tumor as of 2008, according to the National Institutes of Health, with about 44,000 new cases of primary tumors reported each year. Primary brain tumors account for about 2.5 percent of cancer deaths in the United States each year—about 13,000 adults and children. About 100,000 Americans die each year of metastatic brain tumors.
Brain tumors are the most common type of solid tumor in children, and the second most common type of cancer in those below age fifteen. Between 15 and 25 percent of all cancers in children are brain tumors. The most common type of brain tumor in children is called a medullablastoma, a highly malignant cancer that develops in the cerebellum (the part of the brain just above the brain stem). This type of tumor is rare in adults.
Most types of brain tumors are equally common in men and women; however, meningiomas occur slightly more often in women than in men. Medulloblastomas are more common in boys than in girls. And although most brain tumors are more common in Caucasians, meningiomas are more common in African Americans than in members of other races.
Risk factors for brain tumors include:
- Age. Most brain tumors, whether benign or malignant, occur in adults over age forty-five. Brain tumors in children are rare within the first year of life; they occur most often in children between five and eight years of age.
- Exposure to nuclear radiation or radiation therapy for another type of cancer.
- Family history of brain tumors.
- Exposure to certain chemicals.
The causes of primary tumors of the brain were not completely understood as of 2008; most researchers, however, think that defective genes are
responsible. Other theories include viruses, exposure to certain chemicals, and disorders of the immune system.
Secondary brain tumors result from the spread of cancer that began elsewhere in the body, with lung cancer the most common type. Brain tumors can also develop from cancerous cells from the breast, kidneys, colon, or skin. The cancerous cells break off from the primary tumor and travel to the brain through the bloodstream.
The symptoms of a brain tumor may result from a primary tumor; they may also be the earliest symptoms of a cancer that developed in another organ. The most common warning signs include:
- Headaches, which may be most severe in the morning, new for the person, or grow worse over time
- Nausea and vomiting
- Problems with eyesight, such as seeing double or having blurred vision
- Loss of sensation in an arm or leg, or weakness or paralysis on one side of the body
- Difficulty thinking or speaking, having trouble finding words
- Memory loss, confusion, or disorientation
- Seizures or convulsions
- Personality changes
- Hearing loss
- Difficulty walking normally, losing one's balance, frequent falls
- Weakness and fatigue
Symptoms of brain tumors in small children may include:
- Increased head size
- In infants, bulging of the soft spot at the top of the skull
- Breathing problems or problems swallowing
Headaches are the single most common symptom of brain tumors in older children and adults, and the one most likely to bring patients to see their doctor—particularly if the headaches are unusually severe or more frequent than those that the person has experienced in the past.
Diagnosing a brain tumor requires a series of tests and examinations.
- A family doctor will usually refer the patient to a neurologist, a doctor who specializes in treating disorders of the nervous system. The neurologist will check the patient's balance, vision, hearing, reflexes, coordination, ability to speak clearly, changes in mood, and ability to answer simple questions. These tests help to locate the areas of the brain that might be affected by a tumor.
- Imaging tests. These include computed tomography (CT) scans, magnetic resonance imaging (MRI), and positron emission tomography (PET).
- Electroencephalogram (EEG). This is a test that shows the levels of electrical activity in different parts of the brain.
- Blood and urine tests. These are used to monitor the patient's response to treatment for the tumor.
- Tests for cancer in other organs, since most brain cancers are meta-static rather than primary tumors.
- Biopsy. A biopsy is a procedure in which a sample of tissue is removed for study under a microscope. For a brain tumor, the biopsy may be done as part of an operation to remove the tumor or as a separate procedure.
Treatment of brain tumors depends on their grade and location. Surgery is usually the first stage. Removing as much of the tumor as possible helps to relieve symptoms as well as slow the growth of the tumor. Some Grade I tumors can be completely removed by surgery.
If the tumor is located in a part of the brain where it cannot be entirely removed by surgery without risk to the brain stem or other parts of the brain that control sight or hearing, or if the tumor is difficult to distinguish from surrounding healthy tissue, the second line of treatment is usually radiation therapy.
Chemotherapy can be given before or after radiation therapy. A newer type of chemotherapy is combined with surgery. After removing as much of the tumor as is possible and safe, the surgeon inserts wafers containing slow-release anticancer drugs.
Treatment for brain tumors may also include rehabilitation therapy for physical aftereffects and supportive therapy to help the patient manage pain and the side effects of cancer treatment.
The prognosis of a brain tumor depends on whether the tumor is benign or malignant, its location and grade, and the patient's age and overall health. Patients with Grade I tumors that can be entirely removed may recover completely. The prognosis is poorer in very young children and in elderly patients.
The five-year survival rate for patients with malignant primary tumors is less than 10 percent even when these cancers are treated aggressively. Most patients with metastatic brain cancer die as a result of the primary cancer rather than from the metastases in the brain.
Primary brain tumors are not preventable. Some metastatic brain tumors may be prevented by not smoking, which lowers the risk of lung cancer, or by avoiding overexposure to the sun, which lowers the risk of melanoma.
The number of brain tumors diagnosed each year in both adults and children in the United States has been gradually increasing since the 1960s. The reasons for this increase are not yet clear. Theories include toxins in the environment, viruses that have not yet been identified, and heavy long-term use of cell phones.
Some newer treatments for brain tumors that are currently considered experimental include drugs that block the growth of blood vessels in tumors, thus starving them of nutrients. Other new drugs are intended to make radiation therapy more effective by sensitizing the tumor cells to radiation. Gene therapy and biological therapy (which works by stimulating the patient's immune system) are other rapidly expanding areas of research in treating brain tumors.
SEE ALSO Alcoholism; Breast cancer; Colorectal cancer; Headache; Lung cancer; Skin cancer
WORDS TO KNOW
Benign: Not cancerous.
Brain stem: The lowest part of the brain that connects directly to the spinal cord. It controls such basic life functions as breathing, blood pressure, and heart beat.
Cerebellum: The part of the brain at the lower back of the head just above the brain stem.
Glial cells: Cells in brain tissue that hold nerve cells in place, supply them with oxygen and nutrients, and remove dead nerve cells.
Glioma: A type of brain tumor that starts in the glial cells.
Hydrocephalus: Abnormal buildup of cerebrospinal fluid within the brain.
Medulloblastoma: A type of malignant brain tumor that develops in the cerebellum. It is the cancer.
Meninges (singular, meninx): The protective membranes that cover the brain and spinal cord.
Meningioma: A type of brain tumor that starts in the meninges.
Metastasis (plural, metastases): The spread of a cancer from its original location to other organs or parts of the body.
Tumor: An abnormal mass or growth of tissue that may be either cancerous or noncancerous.
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American Brain Tumor Association (ABTA). Diagrams and Videos. Available online at http://www.abta.org/index.cfm?contentid=146 (accessed on September 5, 2008). Page contains links to eight diagrams of the various parts of the brain as well as several videos and audio recordings about tumors.
American Brain Tumor Association (ABTA). Tumor and Treatment Info. Available online at http://www.abta.org/index.cfm?contentid=12 (accessed on September 5, 2008). Detailed information about specific types of brain tumors can be found on the menu at the right.
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