Leukemia - Chronic Lymphocytic (CLL)
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Leukemia is a cancer of the blood. Leukemia begins when normal blood cells change and grow uncontrollably. Chronic lymphocytic leukemia (CLL) is a cancer of the lymphocytes, a type of white blood cell involved in the body's immune system. Lymphocytes are normally found in the blood, lymph nodes, bone marrow (the spongy, red tissue in the inner part of the large bones), spleen, and in a clear fluid called lymph that flows through small vessels in the body and collects in lymph nodes.
In people with CLL, mature lymphocytes grow abnormally and build up in the peripheral (circulating) blood, bone marrow, spleen, and lymph nodes. Over time, these malignant (cancerous) cells may crowd healthy blood-forming cells, resulting in fewer red blood cells (which deliver oxygen to the body), neutrophils (a type of white blood cell needed to fight infection), and platelets (which prevent bleeding). In about half of people, CLL grows and progresses slowly, and it may take years for symptoms to appear or for treatment to be needed. In fact, some patients never require treatment for their CLL. The other half has a more rapidly growing type of CLL, which requires treatment sooner.
There are two general types of CLL, and it is important for doctors to find out whether the disease is caused by the overgrowth of T cells or B cells. T cells and B cells are specific types of lymphocytes. T cells normally help to fight infections by activating other cells in the immune system, while B cells help make antibodies to fight disease. The T-cell type of CLL is less common (about 1% of all CLL cases) and progresses more rapidly than the B-cell type of the disease (more than 95% of all CLL cases).
Learn more about other, rare types of chronic T-cell leukemia.
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In 2009, an estimated 15,490 people of all ages (9,200 males and 6,290 females) in the United States will be diagnosed with CLL. CLL is the most common type of leukemia diagnosed in adults. It is estimated that 4,390 deaths (2,630 males and 1,760 females) will occur in 2009.
The survival rate of people with CLL varies according to the stage of the disease (see Staging) and can range from about one year to more than 20 to 30 years. The overall five-year relative survival rate (percentage of people who survive at least five years after the cancer is detected, excluding those who die from other diseases) of people with CLL is about 76%.
Cancer survival statistics should be interpreted with caution. These estimates are based on data from thousands of cases of this type of cancer in the United States each year, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with CLL. Because the survival statistics are measured in five-year intervals, they may not represent advances made in the treatment or diagnosis of this cancer.
Statistics adapted from the American Cancer Society's publication, Cancer Facts & Figures 2009.
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