Chronic Lymphocytic Leukemia (CLL)

Chronic Lymphocytic Leukemia (CLL)

Chronic lymphocytic leukemia occurs when, in the bone marrow, an early form of a lymphocyte suffers a genetic defect. The cell fails to go through a normal life cycle and multiplies, leading to an overload of white blood cells in the bone marrow. The cells may eventually move out of the bone marrow and into the bloodstream, and then collect in the spleen, liver, or lymph nodes. The cells may look normal and some may work properly, but most are unable to carry out their usual functions.

In most cases of CLL, the affected cells are of the B-cell type. The rest are rare T-cell types, such as natural killer (NK) cell leukemia.

In CLL, the cells that accumulate do not affect the development of other blood cells as much as in other types of leukemia. Because of this difference, early symptoms usually are not as severe as those found in acute leukemia.

CLL also progresses much slower than acute forms of the disease. There is a greater number of mature cells present than in acute forms and those cells are able to perform some of their functions. Over time, however, the cells will lose their ability to work properly.

Symptoms

CLL can develop very slowly, causing no noticeable symptoms for quite some time. About 25 percent of all cases are diagnosed in the course of a routine physical examination, when blood tests reveal an abnormally high number of lymphocytes.

In later stages of the disease, the person may feel fatigued or just "not well." They may be short of breath, may lose weight, and may also develop enlarged lymph nodes, a feeling of fullness in the abdomen, night sweats, fever, loss of appetite, anemia, or recurring infections of the skin and respiratory tract.

Who Gets CLL

Chronic lymphocytic leukemia is found almost exclusively in adults, and most often in those over the age of 55. The average age of onset is 70. It is more common in men than in women.

Risk Factors

Known risk factors for CLL include smoking and having a close relative who has the disease. Long-term exposure to some pesticides is also a risk factor for farmers.

Exposure to the chemical benzene or to high doses of radiation, which are known risk factors for other types of leukemia, are not known to be risk factors for CLL.

Risk factors, however, account for only a small percentage of cases of CLL; most people who develop the disease have no risk factors. And even if risk factors do exist, it is rarely possible to say exactly what caused one person's leukemia.

Stages of CLL

When CLL is diagnosed, tests will be done to see how far the disease has progressed. Determining the stage of disease is an important part of treatment planning for CLL, because early stages often require no treatment. Two different staging systems may be used.

Rai Stages

• Stage 0. Blood tests show more than 15,000 lymphocytes per cubic millimeter of blood, a condition called lymphocytosis. No other symptoms are noted.

• Stage 1. Lymphocytosis is present, along with swollen lymph nodes.

• Stage 2. Lymphocytosis is present, along with an enlarged liver or spleen. Swollen lymph nodes may be present.

• Stage 3. Lymphocytosis is present, and the blood contains too few red blood cells. Swollen lymph nodes, an enlarged liver, and an enlarged spleen are also possible.

• Stage 4. Lymphocytosis is present, and platelet levels are below normal.

Binet Stages

The Binet staging system takes into account the number of lymphoid tissue areas in the body that are affected by an overabundance of lymphocytes and whether or not the levels of red blood cells or platelets have dropped abnormally low. The two latter conditions are known as anemia and thrombocytopenia. Lymphoid tissue areas considered in this system include the neck lymph nodes, underarm lymph nodes, groin lymph nodes, and the spleen.

• Stage A. Only one or two lymphoid tissue areas are involved. No anemia or thrombocytopenia is found.
• Stage B. Three or more lymphoid tissue areas are involved. No anemia or thrombocytopenia is present.
• Stage C. Any number of lymphoid tissue areas are involved, and both anemia and thrombocytopenia are present.

Immunophenotype

The immunophenotype, or what early blood cell line the disease arose in, is another important characteristic. Most cases of CLL are of the B-cell type, meaning the disease developed in the B-cell lymphocyte cell line. A very small percentage are the T-cell type. This subtype of disease, known as T-cell chronic lymphocytic leukemia, can progress faster than the other type. Some patients are also found to have NK cell type, meaning that the disease developed in the cell line that produces natural killer cells.

Prognostic Factors

Some unfavorable prognostic factors for CLL include some chromosomal changes, involvement of several areas of bone marrow, and certain findings on laboratory tests.