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Leukemia is a type of cancer that affects the bone marrow, the soft, spongy center of the bone that produces blood cells.
There are three main types of blood cells:
- White blood cells, or leukocytes, help the body fight infections and other diseases.
- Red blood cells, or erythrocytes (which contain hemoglobin), 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 that 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 they move into the body, they can collect in different places, causing swelling or pain.
Leukemia accounts for nearly one-third of cancer cases in children under age 15. However, like most other forms of cancer, it is much more common in adults. In 2006 roughly 35,070 adults and 2,800 children will be diagnosed with leukemia.
Over the past 20 to 30 years, great strides have been made in treating leukemia. The death rate for children with leukemia has declined nearly 60 percent, and about 20 percent for adults younger than 65. Thus, what was once an often-fatal disease is now treatable in many cases, thanks to the success of the clinical trials that have discovered new treatment approaches.
Different types of leukemia are described according to how quickly the disease develops and by the type of blood cell affected.
This article was reviewed and updated June 2007.
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