About Acute Myelogenous Leukemia (AML)

Every year, approximately 10,600 new cases of acute mylogenous leukemia (AML) are diagnosed in the United States. That's about 2.3 cases for every 100,000 people. AML affects adults much more often than it does children, with people over the age of 65 falling into the highest risk group.

 

Acute myelogenous leukemia occurs when immature blood cells called myeloblasts fail to mature into the different types of blood cells, a process called differentiation. Healthy myeloblasts differentiate into white blood cells, platelets and red blood cells.

If differentiation doesn't occur, myeloblasts accumulate in the bloodstream where they eventually outnumber healthy blood cells. From the bloodstream, the cancer can spread into the liver, the spleen, or any other organ in the body.

A blood count of at least thirty percent myeloblasts is required for a diagnosis of acute myelogenous leukemia. Mature white blood cell counts may be high, low or normal. Platelets, the cells responsible for normal blood clotting, are usually at lower than normal levels.

A number of tools are used to diagnose AML, including blood tests and bone marrow biopsies.

Once AML is diagnosed, the disease is further classified into one of eight different subtypes, each described according to the abnormal cell's morphology. Cell morphology is how the cells appear under a microscope. The disease is then classified into FAB (French-American-British) subtypes.

FAB subtypes are referenced by letter and number. For AML, the letter is M, and the sub-types are M0 to M7. (See the AML Classification Subtypes section below for a list of the FAB types.) Because different sub-groups of leukemia respond to different treatments, identifying the disease's FAB classification is vital.

Without treatment, AML often proves fatal within three to four months. Prompt treatment greatly increases a patient's chance of survival. Seventy to eighty percent of treated cases result in remission—the reduction or disappearance of cancer symptoms.

Once remission is achieved, further "consolidation" treatments are given to attempt a permanent cure. Overall, twenty to thirty percent of people who go into remission are free of symptoms five years later. Those figures rise to between forty and fifty percent for younger people. The cancer is considered cured if the patient has not experienced a relapse after two years of remission.

Certain factors affect AML's prognosis. People under the age of fifty who have FAB types M2, M3 or M4 are most likely to be cured of the disease. Negative factors include being over age fifty, having high white blood cell levels at the time of diagnosis and a history of prior treatment for leukemia. FAB type M7 and the presence of drug-resistant genes are also negative factors.

Chromosomal alterations can affect prognosis, although the role they play is complicated. While some chromosomal alterations may worsen the prognosis, others can actually improve the chances of remission and cure.

The FAB subtypes are:

Resources

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Graham, C., Mehta, P., & Fulper-Smith, M. (updated 2001). Acute myelogenous leukemia. Arkansas Cancer Research Center.

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Leukemia and Lymphoma Society. (updated 2002). Acute myelogenous leukemia.

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