Leukemia (lo-KEY-me-a) is a type of cancer in which the body produces a large number of immature, abnormally shaped blood cells. It usually affects the white blood cells, or leukocytes (LOO-ko-sites), which help the body fight infections and other diseases.
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Acute lymphocytic leukemia
Bone marrow transplantation
Sam had been looking forward to the basketball season for weeks. Now that it had actually started, though, he was having trouble keeping up during practice and in games. He just did not have the energy that he usually had, and he felt pain in his joints like never before. He found that he always needed to ask the coach to give him breaks during games. His teammates accused him of being out of shape, but Sam knew that it was more than that. His mother noticed that, even though he was playing less, he had more bruises than he did last season. Eventually, Sam was forced to sit out for a few weeks with a bad case of what appeared to be the flu. He felt constantly weak and tired, and he kept getting fevers. His mother decided that it was time to see the doctor and figure out what was going on.
After hearing about Sam's symptoms, the doctor ran some blood tests. These showed that Sam had leukemia, and further testing indicated that it was a type called acute lymphocytic (lim-fo-SIT-ik) leukemia, or ALL. This is the most common type of leukemia in children.
Overall, leukemia accounts for about one third of cancer cases in children. However, like most other types of cancer, it is much more common in adults. Each year, roughly 27,000 adults and 2,000 children in the United States are diagnosed with leukemia.
What Is Leukemia?
Leukemia is a type of cancer that affects the bone marrow, the soft, spongy center of the bone that produces blood cells. White blood cells, or leukocytes, help the body fight infections and other diseases. Red blood cells, or erythrocytes (e-RITH-ro-sites), carry oxygen from the lungs to the body's tissues and take carbon dioxide from the tissues back to the lungs. Platelets help form blood clots that control bleeding.
These cells are normally produced in an orderly, controlled way as the body needs them, but with leukemia, the process gets out of control. In most cases, the marrow produces too many immature white blood cells (called blasts), that are abnormally shaped and cannot carry out their usual duties. This explains why the disease is called "leukemia," which literally means "white blood." As these blasts multiply and crowd the bone marrow, they interfere with the production of other types of blood cells. When the blasts move into the body, they can collect in different places, causing swelling or pain.
Different types of leukemia are described according to how quickly the disease develops and what type of blood cell is affected:
- Acute (a-KUTE) leukemia gets worse quickly, with fast multiplication of abnormal, immature blasts.
- Chronic (KRON-ik) leukemia worsens gradually. Abnormal blasts are present, but they are more mature and can carry out some of their functions.
- Lymphocytic leukemia affects certain white blood cells called lymph-ocytes (LIM-fo-sites), which control the body's immune response by finding and destroying foreign substances.
- Myelogenous (my-e-LOJ-e-nus) leukemia affects other types of white blood cells in the bone marrow.
In all, there are four main forms of the disease: acute lymphocytic leukemia (ALL), acute myelogenous leukemia (AML), chronic lympho-cytic leukemia (CLL), and chronic myelogenous leukemia (CML). Another less common form is called hairy cell leukemia, a chronic condition in which the cells develop projections that look like tiny hairs.
What Causes Leukemia?
In most cases of leukemia, doctors cannot pinpoint a specific cause. However, researchers have identified a few possible risk factors * . Studies have shown that people who are exposed to high or repeated doses of radiation * , such as Japanese survivors of the atomic bomb dropped at Hiroshima, and people with other types of cancer who have been treated with radiation therapy * , are more likely to develop leukemia. Workers who are exposed to certain chemicals, such as the benzene found in gasoline, also develop leukemia more frequently. In addition, certain viruses may play a role in the disease, although this is still under investigation.
Researchers also are studying how a person's genes * may be involved in causing leukemia. In studying the cells of people who have the disease, researchers have found that they often share certain genetic abnormalities.
Some people have suggested a possible connection between childhood leukemia and the low-energy waves given off by high-voltage electric power lines. However, recent studies have not shown a relationship.
What Are the Symptoms of Leukemia?
When someone has leukemia, the abnormal, immature white blood cells that form cannot help the body fight off infections. As a result, the person may have frequent infections and develop flu-like symptoms, such as fever and chills. As these cells keep multiplying and move out into the body, they tend to collect in the lymph nodes * or in organs such as the liver * or spleen * . This may cause pain and swelling. If the cells collect in the central nervous system (the brain and spinal cord), they may cause headaches, vomiting, confusion, loss of muscle control, or seizures.
Many of the terms associated with leukemia, including the name of the disease itself, are derived from the Greek language. Breaking down the words into their Greek roots makes them easier to understand.
- Leuk- or leuko- means white or colorless and is used to form the words "leukemia" and "leukocyte."
- -emia means blood and is found in the words "leukemia" and "anemia."
- -cyte means cell and is used to form the words "leukocyte," "erythrocyte," and "lymphocyte."
- Erythr- or erythro- means red. "Erythrocytes" are red blood cells.
- Chron- or chrono- means time. "Chronic" leukemia develops over a long period of time.
* risk factors are anything that increases the chance of developing a disease.
* radiation is energy that is transmitted in the form of rays, waves, or particles. Only high-energy radiation, such as that found in x-rays and the sun's ultraviolet rays, has been proven to cause human cancer.
* radiation therapy is a treatment that uses high-energy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths.
* genes are chemicals in the body that help determine a person's characteristics, such as hair or eye color. They are inherited from a person's parents and are contained in the chromosomes found in the cells of the body.
The oversupply of white blood cells also interferes with the normal production of red blood cells and platelets, causing bleeding problems and a disorder called anemia (a-NEE-me-a). The person may look pale or feel weak and tired. They also may bleed or bruise easily, or find that their gums are swollen or bleeding. Other possible symptoms of leukemia include loss of appetite and/or weight; tiny red spots under the skin; sweating, especially at night; and bone or joint pain.
How Is Leukemia Diagnosed?
Doctors who see patients with these symptoms usually start by doing a full physical exam and feeling for swelling in the liver, the spleen, and the lymph nodes under the arms, in the groin, and in the neck. They also may take a sample of blood and examine it under a microscope to see what the cells look like and to determine the number of mature cells versus immature cells. Although blood tests may reveal that a patient has leukemia, they may not show what type it is. Another test called bone marrow aspiration may be necessary to check further for leukemia cells or to tell what type of leukemia a patient has. In this test, the doctor inserts a needle into a large bone, usually the hip, and removes a small sample of bone marrow. The sample then is examined under a microscope for leukemia cells.
If leukemia is present, the doctor may order additional tests to look for abnormal cells in other parts of the body. A spinal tap involves taking a sample of the fluid that fills the spaces in and around the brain and spinal cord, so that it can be checked for leukemia cells. Chest x-rays and special scans can reveal signs of the disease elsewhere in the body.
How Is Leukemia Treated?
Once acute leukemia is diagnosed, doctors start treating it right away, because it tends to worsen quickly. The goal is to bring about a complete remission, which means that there is no evidence of leukemia in the bone marrow or blood. Then doctors can give further treatment to help prevent a relapse, which means a return of the signs and symptoms of the disease after a period of improvement. Many people with acute forms of leukemia can be cured today. Just a few decades ago, ALL was considered incurable, but now it is one of the most curable forms of cancer.
Chronic leukemia sometimes is detected through a routine blood test before symptoms appear. People with chronic leukemia may not need treatment right away if they are not having symptoms yet. Doctors monitor the disease until treatment is needed. It usually can not be cured, but it can be controlled.
* lymph nodes are round masses of tissue that contain immune cells that filter out harmful microorganisms.
* liver is a large organ located in the upper abdomen that cleanses the blood and aids in digestion by secreting a substance called bile.
* spleen is an organ near the stomach that helps the body fight infections and use red blood cells effectively.
The most common treatments for leukemia are chemotherapy (kee-mo-THER-a-pee), radiation therapy, and/or bone marrow transplantation. In chemotherapy, patients take one or more anticancer drugs by mouth or intravenously, through a tube in one of the veins. In certain cases, doctors need to inject the drugs directly into the fluid that surrounds the brain and spinal cord. Chemotherapy can cause side effects, such as hair loss, nausea, fatigue, or easy bruising, depending on the drugs used. Most side effects go away gradually between treatments or after treatment stops.
In radiation therapy, doctors use a special machine to deliver high-energy rays that damage cancer cells and stop them from growing. The rays may be directed to one specific area of the body where leukemia cells have collected, such as the spleen, or to the whole body. Like chemotherapy, radiation therapy can cause temporary side effects, such as fatigue, hair loss, nausea, or red, dry, itchy skin.
Bone marrow transplantation
In bone marrow transplantation, doctors give high doses of chemotherapy and radiation to destroy all of the patient's bone marrow, in order to kill the cells that are the source of the cancer. Then they give the patient healthy bone marrow from a donor whose tissue is similar, ideally from an identical twin or sibling. They also might give bone marrow that was removed from the patient earlier and specially treated to remove any leukemia cells. A patient who has a bone marrow transplant usually stays in the hospital for several weeks. The risk of infection is high until the transplanted bone marrow begins to produce enough white blood cells.
The newest form of treatment under investigation is called biological therapy, which uses substances produced by the body to increase its ability to fight off leukemia. Scientists have identified several substances that are involved in the immune response, which is the body's way of protecting itself from infections and other diseases. Today scientists can produce some of these substances in the lab and use them to help the body defend itself against leukemia and other forms of cancer.
Living with Leukemia
Living with leukemia can be difficult. Not only can the disease make someone feel sick, but the treatments can, too. Fortunately, though, these treatments often make the disease go into remission. Once this happens, patients still need to see their doctors often for follow-up visits and tests. That way, if the leukemia comes back, it will be detected as quickly as possible.
Having leukemia can be difficult emotionally, too. It is scary for patients to find out that they have a form of cancer and to worry about what the future may hold. Some people withdraw, get angry, or get depressed when they are diagnosed with leukemia. However, with the support of family, friends, support groups, and health professionals, a spirit of realistic optimism can win out.
Keene, Nancy. Childhood Leukemia: A Guide for Family, Friends, and Caregivers. Sebastopol, CA: O'Reilly and Associates, 1997. This book is written mainly for parents, but it offers a wealth of practical advice on coping with childhood leukemia.
American Cancer Society, 1599 Clifton Road Northeast, Atlanta, GA
30329-4251. This large nonprofit organization provides information about
leukemia in both children and adults.
Leukemia Society of America, 600 Third Avenue, New York, NY 10016. This
nonprofit organization provides extensive information about leukemia to
National Bone Marrow Transplant Link, 29209 Northwestern Highway, Number
624, Southfield, MI 48034. A support organization for bone marrow
U.S. National Cancer Institute, Building 31, Room 10A03, 31 Center
Drive, Bethesda, MD 20892-2580. This U.S. government agency provides
detailed information about leukemia and posts a fact sheet
What You Need to Know About Leukemia
at its website.