Understanding Chronic Myelogenous Leukemia (CML)

Chronic myelogenous leukemia, or CML, is an uncommon form of leukemia that starts in the blood-forming cells of the bone marrow. About 4,800 new cases of this type of chronic leukemia are diagnosed each year, according to the Mayo Clinic (2008).

CML occurs most often in older adults and rarely affects children. Risk factors include older age, being male and radiation exposure. Learn the distinctions between the various types of leukemia and how CML is treated.

Types of Leukemia

Two types of leukemia exist, which differ when it comes to disease progression:

• Acute leukemia is characterized by immature cells that grow quickly, but don't develop properly. These cancerous cells continually split off to form new cells and build up in the blood. Without treatment, most people with acute leukemia only live a few months. Luckily, many forms of acute leukemia respond well to treatment, and many people can expect to be cured, or in remission.
• Chronic leukemia involves cells that appear to be mature, but aren't. These cancerous cells live longer than they should and build up, crowding out healthy normal cells in the bone marrow space. Chronic leukemia progresses more slowly than the acute type, enabling most patients to live for many years. However, chronic leukemia is often more difficult to treat.

Leukemia can also be classified as myeloid or lymphocytic. Lymphocytic leukemia begins in the lymphocytes, a type of white blood cell. Myeloid leukemia starts in other types of white blood cells, as well as cells that mature into platelets or red blood cells. Both lymphocytic and myeloid leukemia can present in either acute or chronic forms.

How Chronic Myelogenous Leukemia Develops

Chronic myelogenous leukemia begins when certain unexplained genetic changes in blood cells occur.

An abnormally short chromosome 22 — termed the "Philadelphia chromosome," since it was discovered in Philadelphia — develops when a section of chromosome 9 switches places with a section of chromosome 22. The Philadelphia chromosome goes on to create a new gene, called BCR-ABL. This abnormal gene triggers the production of a protein that allows certain blood cells to grow uncontrollably, resulting in CML.

Symptoms of Chronic Myelogenous Leukemia

The early stages of chronic myelogenous leukemia are often asymptomatic. In fact, many people have CML for months or even years without being aware of it. When symptoms are present, however, they may include:

• Bleeding easily
• Fatigue
• Fever
• Frequent infections
• Night sweats
• Pain or fullness on the left side, below the ribs
• Pale skin
• Poor appetite and weight loss.

A CML diagnosis requires blood and bone marrow tests, as well as a physical examination.

Treating Chronic Myelogenous Leukemia

For most chronic myelogenous leukemia patients, treatment aims to reduce the number of abnormal cells to achieve a long-term remission, rather than completely rid the body of these cells. Some widely used treatments for this type of chronic leukemia include:

• Biologic therapy, including interferon
• Blood stem cell transplants
• Chemotherapy
• Drugs that target the protein produced by the BCR-ABL gene.

Resources

American Cancer Society. (2010). Leukemia: Chronic myeloid (myelogenous) overview. Retrieved October 26, 2010, from http://www.cancer.org/Cancer/Leukemia-ChronicMyeloidCML/OverviewGuide/index.

Mayo Clinic. (2008). Chronic myelogenous leukemia. Retrieved October 26, 2010, from http://www.mayoclinic.com/health/chronic-myelogenous-leukemia/DS00564.