LEUKEMIA

DEFINITION

Leukemia (pronounced loo-KEE-mee-uh) is a form of cancer (see cancer entry) in which the body produces too many white blood cells. Many forms of leukemia have been identified. They are divided into two general types: acute and chronic. An acute condition comes on fairly quickly. A chronic disorder develops more slowly over time.

DESCRIPTION

Blood contains three types of cells: red blood cells, white blood cells, and platelets (pronounced PLATE-lits). Each type of cell has a special function in the body. Red blood cells carry oxygen from the lungs to the rest of the body. White blood cells fight invading organisms, such as bacteria and viruses. Platelets are involved in the process of blood clotting.

All blood cells form in the soft tissue that fills the center of bones. This tissue is called bone marrow. All three types of blood cells arise out of a primitive type of cell known as a stem cell. A stem cell can develop into a red blood cell, a white blood cell, or a platelet, depending on conditions.

Leukemia is caused by the overproduction of white blood cells. This has two effects on the body. First, the white blood cells may not mature properly as they develop. They may lack the ability to kill foreign bodies in the bloodstream. This defect seriously damages the immune system and the body loses its ability to fight off infections.

Second, so many white blood cells may form that they pack the bone marrow until there is not enough room for red blood cells and platelets to develop. Without red blood cells, the body's cells do not get enough oxygen, and the condition known as anemia (see anemias entry) develops. Anemia is characterized by general weakness, headache, pale skin, and dizziness. It can become a life-threatening disorder. Without platelets, blood cannot clot properly and simple injuries can lead to serious blood loss.

There are three types of white blood cells. Each has a special role to play in the immune system. The three types are granulocytes (pronounced GRAN-yuh-lo-site), lymphocytes (pronounced LIM-fuh-sites), and monocytes (pronounced MON-uh-sites). Leukemia may result in the overproduction of any one type of white blood cell. Each type of leukemia is named for two characteristics:

• Whether it is acute or chronic
• Whether it affects granulocytes, lymphocytes, or monocytes

For example, one form of leukemia develops very slowly. It results in the overproduction of granulocytes. That form of leukemia is called chronic granulocytic leukemia. The same disease is also known by another name, chronic myelogenous (pronounced my-uh-LAJ-uh-nuhs) leukemia.

Another form of leukemia occurs rapidly. It results in the overproduction of lymphocytes. That form of leukemia is called acute lymphocytic leukemia.

Leukemias account for about 2 percent of all cancers. It is the most common form of cancer among children. For that reason, leukemia is sometimes called a disease of childhood. However, leukemias affect nine times as many adults as children. Half of all cases of the disease occur in people over sixty. The incidence of acute and chronic leukemias is about the same.

CAUSES

No one knows what causes leukemia. Researchers have strong suspicions about four possible causes, however. They are radiation, chemicals, viruses, and genetic factors.

• Radiation. The term "radiation" refers to various forms of energy, such as X rays and ultraviolet (UV) light found in sunlight. Radiation can tear chemicals apart, thus damaging or destroying cells. Some researchers believe that exposure to radiation can cause some forms of leukemia.
• Chemicals. Some types of chemicals are known to be carcinogens (pronounced car-SIN-o-genz). A carcinogen is anything that can cause cancer. Chemicals can cause cancer by damaging cells and the substances within them.
• Viruses. Some researchers believe that some types of leukemia are viral infections. A virus is a very small organism that can cause a disease. The link between viruses and leukemia is strong in some cases, but it has not been proved.
• Genetics. Leukemia tends to occur in some families more commonly than in others. This suggests that at least some forms of leukemia may be hereditary.

Acute myelogenous leukemia cancer cells. (Photograph by

Robert Becker

. Reproduced by permission of

Custom Medical Stock Photo

.)

SYMPTOMS

The symptoms of leukemia are generally vague. A patient may experience all or some of the following symptoms:

• Weakness or chronic fatigue
• Fever of unknown origin
• Unexplained weight loss
• Frequent bacterial or viral infections
• Headaches
• Skin rash
• Bone pain with no known cause
• Easy bruising
• Bleeding from gums and nose
• Blood in urine or stools
• Enlarged lymph nodes and/or spleen
• Fullness in the stomach

DIAGNOSIS

The first step in diagnosing leukemia occurs when a patient sees a doctor for one or more of the described symptoms. The doctor must then try to find the cause of these symptoms. The doctor first performs tests to rule out other medical conditions.

The first specific test for leukemia is likely to be a blood test. A blood test shows the relative amounts of red and white blood cells. An unusually large number of white blood cells might suggest the possibility of leukemia.

A more specific test is a bone marrow biopsy. A bone marrow biopsy is conducted with a long, thin needle that is inserted into the marrow of a bone. A bone in the hip or chest is usually chosen for this procedure. A sample of

Chronic lymphocytic leukemia cells magnified 400 times. (© 1999. Reproduced by permission of

Custom Medical Stock Photo

.)

the bone marrow is removed and studied under a microscope. The presence of abnormal blood cells is the basis for diagnosing leukemia.

If there is still doubt, an additional test may be performed. This test is a lumbar puncture (spinal tap). In a lumbar puncture, a thin needle is inserted into the space between vertebrae in the patient's spine. A sample of cerebrospinal fluid is withdrawn. Cerebrospinal fluid is a liquid that surrounds the tissues in the brain and spine. The presence of abnormal blood cells indicates that the patient has leukemia.

TREATMENT

Treatment of leukemia takes place in two steps. The goal of the first step is to bring the disease into remission. Remission means two things. First, no symptoms of the disease remain. Second, no abnormal white blood cells can be found in bone marrow. Two forms of treatment are used in this first step: chemotherapy and radiation.

Chemotherapy involves the use of certain chemicals that can kill cancer cells. These chemicals may be given orally (by mouth) or intravenously (through a vein in the arm).

Radiation involves the use of high-energy rays, such as X rays, to kill cancer cells. A common source of radiation used to treat leukemia is the radioactive element cobalt 60. A radioactive element is an element that gives off high-energy radiation. A patient is placed on a table beneath a small piece of cobalt 60 contained in a large machine. The energy given off by the cobalt 60 is aimed at the patient's body. It kills cancer cells and may lead to remission.

Once remission has been achieved, treatment moves to the second step. The goal of this step is to treat the patient's bone marrow. Unless the bone marrow is changed, it will continue to produce abnormal white blood cells and the leukemia will eventually return.

The usual method for treating bone marrow is with a bone marrow transplantation. In a bone marrow transplantation, healthy bone marrow is injected into the patient's bones. If the transplantation is successful, the new bone marrow will start producing normal blood cells and the basic cause of leukemia will have been corrected.

Bone marrow transplantation is a difficult procedure. The bone marrow injected into a patient must be very similar to his or her own bone marrow. For this reason, close relatives may be the only people who can donate bone marrow for the procedure.

If foreign bone marrow is used for transplantation, the patient's immune system will attack it as if the transplanted bone marrow is a bacterium, virus, or some other disease-causing organism. In the process, the patient's immune system may start to kill off the cells in his or her body. There are drugs that can prevent this type of immune system reaction, but the drugs are quite dangerous and have serious side effects.

Alternative Treatment

Many alternative treatments are available that may prove helpful in combating the side effects of traditional cancer therapies. These alternatives, however, should not replace prescribed cancer treatments; rather, they are suggested to work in conjunction with conventional treatment.

Body work therapy such as acupuncture (Chinese therapy involving the use of fine needles), acupressure (Chinese therapy that involves applying pressure to certain points in the body), reflexology, and massage may help calm the patient and reduce stress. Relaxation techniques such as yoga and meditation may relieve nausea and discomfort. An exercise program, designed in consultation with a physician, may help promote physical and mental strength. A well-balanced diet high in fresh fruits and vegetables and whole grains and low in fats, sugar, and alcohol is suggested for overall well-being.

PROGNOSIS

The prognosis for various forms of leukemia varies widely. Three important factors are the patient's age and general health, and the time since diagnosis. That is, younger patients who are otherwise in good health have the best chance for survival if their leukemia is diagnosed early.

Prognosis also varies depending on the form of leukemia. In general, patients with chronic forms of the disease tend to live longer than those with acute forms. The average survival rate for patients with chronic leukemia is about nine years. By contrast, only about half of all patients with acute myelogenous leukemia survive five years. For acute lymphocytic leukemia, the survival rate is even less.

Medical progress has greatly improved the prognosis for leukemia over the past thirty years. Surgeons are becoming much more proficient at bone marrow transplantations. As a result, more and more patients face the possibility not only of remission but also a cure.

PREVENTION

Until the cause or causes of leukemia are found, there is no way to prevent the disease.

FOR MORE INFORMATION

Books

Dollinger, Malin. Everyone's Guide to Cancer Therapy. Toronto: Somerville House Books, Ltd., 1994.

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

Siegel, Dorothy Schainman, and David E. Newton. Leukemia. New York: Franklin Watts, 1994.

Organizations

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

Cancer Care, Inc. 1180 Avenue of the Americas. New York, NY 10036. (800) 813–HOPE. http://www.cancercareinc.org.

Cancer Research Institute. 681 Fifth Avenue, New York, NY 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. 31 Center Drive, Bethesda, MD 20892–2580. (800) 4–CANCER. http://www.nci.nih.gov.

Web sites

Oncolink. [Online] University of Pennsylvania Cancer Center. http://cancer.med.upenn.edu (accessed on October 13, 1999).