Chronic lymphocytic leukemia

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Definition

Chronic lymphocytic leukemia (CLL) is a type of cancer of the blood and bone marrow — the spongy tissue inside bones where blood cells are made. It's called chronic leukemia because it progresses more slowly than acute leukemia. It's called lymphocytic leukemia because it affects a group of white blood cells called lymphocytes, which typically fight infection.

Under normal circumstances, your bone marrow produces immature cells (stem cells) in a controlled way, and they mature and specialize into the various types of blood cells, as needed. When these cells grow old, they die naturally and are replaced by new cells, in a continuous cycle. In chronic lymphocytic leukemia, this process goes awry. The bone marrow produces abnormal lymphocytes. These cells don't fully mature or die normally. Over time, they accumulate in large numbers and eventually crowd out other healthy cells, leaving people with chronic lymphocytic leukemia vulnerable to infection and other life-threatening problems.

Each year, about 10,000 people in the United States receive a diagnosis of chronic lymphocytic leukemia. A decade ago, doctors thought chronic lymphocytic leukemia always affected older adults and rarely posed enough risk to warrant cancer treatments, so "watchful waiting" was the treatment of choice. Today, new laboratory tests, new medications and a new understanding of chronic lymphocytic leukemia have dramatically changed the rules for treatment of this type of leukemia. Doctors now know that chronic lymphocytic leukemia can behave aggressively in some people. Although watchful waiting is still the best option for some people, new medications are helping people diagnosed with a more aggressive form of chronic lymphocytic leukemia at a younger age.

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Symptoms