About Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) averages 5,050 new diagnoses a year in the United States, according to the Association of Community Cancer Centers. This type of chronic leukemia most often affects adults, and is slightly more common in men than women. Caucasians also have a higher risk of chronic myelogenous leukemia than Afrian Americans.

Chronic myelogenous leukemia can occur at any age, but unlike some types of leukemia, it rarely affects children younger than age 10. The average age of diagnosis is 45 to 65.

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

Diagnosis of CML

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.

CML Phases

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

• Chronic phase: The earliest stage of chronic myelogenous leukemia, the chronic phase can last for years. The disease is most likely to respond to treatment during this phase.
• Accelerated phase: Abnormal cells begin to increase in number, with a corresponding drop in healthy blood cells.
• Blast phase: Also known as “blast crisis.” Blasts cell numbers rise, increasing the risk for infection. Low platelet levels may cause bruising and bleeding problems, and insufficient red blood cells reduce the amount of oxygen the blood transports. The cancer may spread to the bones or the lymph nodes at this point, and the speed of abnormal cell reproduction resembles AML.

Prognosis

Survival rates for chronic myelogenous leukemia once averaged four to seven years after diagnosis. Treatment with imatinib, a medication that blocks abnormal enzymes associated with CML, has improved survival rates, with over 90 percent of chronic myelogenous leukemia patients surviving at least five years past diagnosis, according to Merck Pharmaceuticals (2008).

Resources

American Cancer Society. (2010). What are the key statistics about chronic myeloid leukemia? Retrieved March 22, 2010, from http://www.cancer.org/Cancer/Leukemia-ChronicMyeloidCML/DetailedGuide/leukemia--chronic-myeloid--myelogenous--key-statistics.

Association of Community Cancer Centers. (n.d.). Treating small-population cancers. Retrieved April 28, 2010, from http://accc-cancer.org/education/education-CML.asp.

Mayo Clinic. (2008). Chronic myelogenous leukemia. Retrieved March 22, 2010, from http://www.mayoclinic.com/health/chronic-myelogenous-leukemia/DS00564.

Merck Manuals Online Medical Library. (2008). Chronic leukemia. Retrieved March 22, 2010, from http://www.merck.com/mmpe/sec11/ch142/ch142c.html?qt=leukemia