About Chronic Lymphocytic Leukemia (CLL)

Chronic lymphocytic leukemia is the most common form of adult leukemia, accounting for approximately 7,000 new cases a year in the United States. Men are twice as likely to develop CLL as women. The key risk factor is age: over 75 percent of CLL cases are diagnosed after age sixty.

 

CLL is a progressive disease for which no cure has been found. The cancer produces abnormal white blood cells that are very long-lived. Instead of the rapid accumulation of white blood cells that characterizes acute forms of the disease, CLL cells are thought to accumulate slowly because of their longer life span. Eventually, the leukemic cells crowd out healthy white blood cells, platelets and red blood cells.

Because the cancer progresses at such a slow rate, and given the lack of a cure, treatment is usually put off until symptoms develop. Watchful waiting, or the careful monitoring of progression and symptoms, is often recommended.

Blood tests for chronic lymphocytic leukemia reveal high levels of white blood cells. Further testing reveals that over thirty percent of the cells in the bone marrow are lymphocytes, an abnormally high percentage.

A blood smear also reveals a high proportion of fragile smudge cells—cells that have been damaged during the spreading of blood onto a slide: their walls rupture, and they are seen under the microscope as smudgy shapes. Smudges are higher for CLL than for other diseases: they comprise over twenty percent of the total lymphocytes. In comparison, in acute leukemia, only one to two percent are smudges.

Immunophenotyping looks for specific cell markers that indicate disease. A classic indication of chronic lymphocytic leukemia is the presence of the surface antigens CD 5, and the combination of CD 19 and CD 20.

Chronic lymphocytic leukemia classification depends on whether the abnormal surface markers resemble B or T lymphoid cells. Eighty-five percent of CLL cases are B cell types, with surface markers CD 19 and 20, while fifteen percent are T cell cases, which are characterized by CD 5.

In addition, two other forms of cancer are considered subtypes of chronic lymphocytic leukemia. Prolymphocytic leukemia is a form of CLL with a much faster disease progression rate. "Hairy cell" leukemia has white blood cells that, when viewed under a microscope, appear to be covered with tiny hairs.

Two CLL staging methods exist: Rai and Binet. Rai is the method most commonly employed in America, while Binet is more common in other parts of the world. Binet stages CLL by measuring the extent of the disease. Rai measures hematologic changes (changes to the blood).

Although no cure exists, the prognosis at the time of diagnosis is not unfavorable. The average survival rate is ten years after diagnosis. As so many people are over sixty when CLL is detected, the disease does not necessarily shorten life expectancy. If the cancer has a Rai score between 0 and II, individuals may survive from five to twenty years without treatment. Stages III and IV have average survival rates of three to four years without treatment.

Rai System of CLL Staging The stages are: Rai 0: CLL with high white blood cell count Rai I: Rai 0 + enlarged lymph nodes Rai II: Rai I + enlarged liver or spleen Rai III: Rai II + anemia Rai IV: Rai III + low platelet count.

Resources

American Cancer Society. (nd). What are the key statistics about chronic leukemia?

American Cancer Society. (nd). What is adult chronic leukemia?

Beers, M. H., & Berkow, R. (ed). Leukemia. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

National Cancer Institute. (updated 2003). What you need to know about leukemia.

American Cancer Society. (nd). What are the key statistics about chronic leukemia?

American Cancer Society. (nd). What is adult chronic leukemia?

Beers, M. H., & Berkow, R. (ed). Leukemia. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

National Cancer Institute. (updated 2003). What you need to know about leukemia.