About Chronic Myelogenous Leukemia (CML)

Chronic myelogenous leukemia (CML) affects one to 1.5 out of every 100,000 people—a figure that translates into about 4,400 new diagnoses a year in the United States. The disease most often affects adults between the ages of forty and fifty.

CML primarily affects the production of granulocytes, the white blood cells responsible for fighting infections. In CML, granulocytes are arrested at various stages of maturity. While the leukemic cells accumulate slowly in the initial stages of the disease, they may begin to reproduce more rapidly in later stages.

A diagnosis of CML usually begins when routine blood tests reveal anomalies. Testing reveals an elevated white blood cell count, with granulocytes at different stages of maturity and development. The patient may also have a low red blood cell count.

Diagnostic testing also looks for evidence of chromosomal translocation, when genetic information from one chromosome switches locations with information on a different chromosome. CML testing looks for evidence of translocation between chromosomes 9 and 22, which results in the abnormal Philadelphia chromosome, named after the city in which it was discovered. The Philadelphia chromosome carries an abnormal protein called the bcr-abl fusion protein. This protein triggers the uncontrolled growth rate associated with CML-affected cells.

Chronic myelogenous leukemia begins slowly, but as it progresses it often begins to resemble the fast-progressing acute leukemia AML. Three phases are used to describe CML:

The prognosis for CML varies with how early the cancer is detected, but overall survival time averages four years from the time of diagnosis. At present, CML is incurable and treatment concentrates on slowing the course of the disease. Once the cancer reaches the blast phase, survival time is measured in months.

Negative prognostic factors include being over sixty years of age and having a high percentage of blasts in the bone marrow and blood. An enlarged spleen and excessively high platelet counts also suggest that the disease is well advanced.

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.

Leukemia and Lymphoma Society. (updated 2003). Chronic myelogenous leukemia.

Leukemia Research Fund of Canada. (nd). What is chronic myelogenous leukemia (CML)?

National Cancer Institute. (updated 2005). Chronic myelogenous leukemia.

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