Leukemia is a blood cell cancer that starts when the blood-producing bone marrow produces abnormal white blood cells. These abnormal cells displace the normally-functioning white blood cells (which fight infection), red blood cells (which carry oxygen from the lungs to all parts of the body) and platelets (which help control bleeding by forming blood clots). As the normal cells are displaced by the malignant cells, the blood is less and less able to carry out its life-sustaining functions. More than 62,000 people in the United States are diagnosed with leukemia each year.
There are several proven risk factors for leukemia. Having one or more of these risk factors does not mean someone is going to develop leukemia. It only means that people with one or more of these factors are more likely to develop the disease.
- Extremely high levels of radiation.
The atomic bomb explosions in Hiroshima and Nagasaki in World War II and the Chernobyl nuclear power plant accident in 1986 led to a higher than normal incidence of leukemia among people exposed to the radiation.
High-dose-rate radiation therapy can also increase the risk of leukemia. Diagnostic imaging radiation (such as x-rays) is not at high enough levels to increase risk.
- Prolonged exposure to benzene or formaldehyde.
- Chemotherapy, especially with alkylating agents.
- Down syndrome.
- Human T-cell leukemia virus. (Presence of this virus elevates the risk of developing leukemia, but it does not appear to be contagious.)
- Myelodysplastic syndrome (a blood disorder).
The warning signs of leukemia can also be symptoms of other conditions. Most people with these symptoms do not have leukemia. However people who experience these symptoms should consult a doctor:
- Night sweats.
- Frequent infections.
- Weakness or fatigue.
- Bleeding easily.
- Bleeding gums.
- Bruising easily (especially purple patches or red spots).
- Bone or joint pain.
- Abdominal swelling or discomfort.
- Swollen lymph nodes.
- Unexplained weight loss.
Detection, Diagnosis and Staging
Leukemia is often detected when patients consult with a doctor about symptoms. The doctor examines the patient to find signs of swelling of the lymph nodes, spleen and liver. Blood tests are performed to see if there are unusually high levels of white blood cells and low levels of red blood cells and platelets, and to find evidence of leukemia damage to the liver and/or kidneys. X-rays may be done to look for signs of leukemia in the chest.
When leukemia is detected one or more of several diagnostic tools are used to diagnose the disease more precisely:
- Biopsy. A hollow needle is used to extract a sample of bone marrow or bone and marrow for microscopic analysis by a pathologist.
- Spinal tap. Fluid is drawn from the spinal column for microscopic analysis by a pathologist.
- Cytogenetics. The chromosomes of cells from peripheral blood, bone marrow and/or lymph nodes are examined.
There are more than a dozen types of leukemia. The ones which occur most frequently are:
- Acute myelogenous leukemia.
- Chronic myelogenous leukemia.
- Acute lymphocytic leukemia.
- Chronic lymphocytic leukemia.
Because leukemia often has spread throughout the body by the time it is detected, the disease is not staged in the four-step system used for most other cancers. The classification system used for leukemia is based on the structure of leukemia cells.
The treatment choices for leukemia depend on the type of leukemia and the extent to which the disease has developed. Patients with chronic leukemia and no symptoms can postpone treatment, but those with acute leukemia need to be treated immediately.
Doctors may recommend watchful waiting for patients with chronic lymphocytic leukemia. With this approach patients are closely monitored, and treatment should begin at once if symptoms appear or the leukemia becomes more aggressive.
Chemotherapy is the most common treatment for leukemia. It may be administered alone or in conjunction with radiation or other treatments. Leukemia chemotherapy is systemic. It goes to all parts of the body. Chemotherapy is administered to leukemia patients in four principal ways:
- Intravenously. Intravenous chemotherapy is administered either by direct injection into a vein or through a catheter which is placed in a large vein and which remains in place throughout the duration of chemotherapy treatments.
- Spinal injection. Because blood vessels filter blood which goes to the brain and spinal cord, orally or intravenously administered chemotherapy may not reach these areas. If leukemia cells are present in these areas, chemotherapy drugs may be injected into the liquid surrounding the spinal cord so the medicine bypasses the mechanism that filters blood going to the brain and spinal cord. The drugs also reach the rest of the body.
- Ommaya reservoir. This method delivers chemotherapy through a catheter in the scalp which bypasses the filtering of blood to the brain and spinal cord. The drugs also reach the rest of the body.
Radiation therapy for leukemia may be either specifically targeted to tumors or spread over the entire body. A linear accelerator generates the radiation field to treat the disease.
Laboratory-produced monoclonal antibodies bind to malignant cells. This treatment, also called immunotherapy, increases the body’s natural defenses against the cancer cells.
Surgery is not used to treat leukemia itself, but if a patient’s spleen has become enlarged as a result of the disease, it may be removed.