Acute Myeloid Leukemia (AML)
Description
Adult acute myeloid or myelogenous leukemia (AML) is a type of cancer in which the bone marrow makes abnormal myeloblasts (a type of white blood cells), red blood cells or platelets. Although rare compared to other types of cancer, such as colon, lung, prostate or breast cancer, adult AML is the most common form of leukemia, with more than 10,000 people diagnosed each year, according to the National Cancer Institute.
AML may be called by several names, including acute myelocytic leukemia, acute myeloblastic leukemia, acute granulocytic leukemia or acute nonlymphocytic leukemia.
AML is a cancer of the blood and bone marrow and develops mainly from two types of white blood cells: granulocytes and monocytes. AML is caused by genetic damage to these developing cells in the bone marrow, resulting in uncontrolled growth and accumulation of undeveloped cells called “leukemic blasts,” which cannot function as normal blood cells. As these cells build up in the bone marrow and blood, there is less room for normal marrow cells, leading to a deficiency of red cells, blood-clotting platelets and normal infection-fighting white cells. When this happens, infection, anemia or easy bleeding may occur.
Symptoms
Possible signs of adult AML include fever, feeling tired, and easy bruising or bleeding. Most patients feel a loss of well-being, may tire easily, or have a pale complexion from anemia. The early symptoms of AML may be like those caused by the flu or other common diseases. A doctor should be consulted if any of the following problems occur: fever, shortness of breath, easy bruising or bleeding, petechiae (flat, pinpoint spots under the skin caused by bleeding), weakness or feeling tired, loss of appetite or weight loss.
Doctors use tests that examine the blood and bone marrow to detect and diagnose adult AML, including:
- physical examination and history
- complete blood count
- number of red blood cells, white blood cells, and platelets
- amount of hemoglobin (protein that carries oxygen) in the red blood cells
- portion of the sample made up of red blood cells
- blood chemistry studies (measuring the amounts of certain substances released into the blood by organs and tissues in the body)
- peripheral blood smear (checking for the presence of blast cells, number and kinds of white blood cells, number of platelets and changes in the shape of blood cells)
- bone marrow aspiration and biopsy (looking for abnormal cells)
- immunophenotyping (identifying cells based on the types of antigens or markers on the surface of the cell to diagnose the subtype of AML).
Once AML has been diagnosed, tests may be conducted to see if the cancer has spread to other parts of the body. The spread of most cancers is usually described as stages. This is not true for acute leukemia. In adult AML, the specific type of AML (there are several) and whether the cancer has spread outside the blood and bone marrow are used to plan treatment instead of the stage. For some types of AML this means doing a lumbar puncture (also know as a spinal tap) to check for leukemia cells that have spread into the spinal fluid.
There is no standard staging system for adult AML; instead the disease is described as untreated, in remission or recurrent. The subtype of the disease is important. Different therapies may be used, and the likely course of the disease and the prognosis may be different.
In untreated adult AML, the disease is newly diagnosed and has not yet been treated. The complete blood count is abnormal, at least 20 percent of the cells in the bone marrow are leukemia cells (blasts), and there are symptoms of leukemia. In adult AML in remission, there are no signs or symptoms of leukemia in the blood, bone marrow, brain, spinal cord or elsewhere in the body. In recurrent adult AML, the cancer has come back after it has been treated. AML may recur in the blood, bone marrow or, rarely, other parts of the body.
The prognosis (chances of recovery) and treatment options depend on the age of the patient, subtype of AML, a test to look for certain DNA changes in the AML cells (the “karyotype” or “chromosome” test) used to determine whether the patient received chemotherapy in the past to treat a different cancer, history of a blood disorder, whether the cancer has spread to the central nervous system and whether the cancer has been treated before.
Common Treatment Options
Standard treatment of untreated adult AML during the remission induction or initial treatment phase depends on the subtype of AML. For most types of AML, beside acute promyclocytic leukemia, or AML M-3, the treatment involves chemotherapy drugs and sometimes special treatments into the spinal fluid. For AML M-3, all-trans retonic acid (ATRA) is used, usually in combination with chemotherapy. AML patients often participate in clinical trials, many of which are offered at the RMBMTP and RMCC. The goal of the initial treatment or induction treatment is to get rid of all the leukemia cells—called remission.
Further chemotherapy treatments are necessary to get rid of the remaining or “hiding” leukemia cells. This treatment is known as “consolidation” therapy. Standard treatment of adult AML during consolidation depends on the subtype of AML and may include combination chemotherapy, high-dose chemotherapy with or without radiation therapy, stem cell transplantation using the patient’s stem cells or high-dose chemotherapy and stem cell transplantation using donor stem cells. The different consolidation treatments are tailored to individual patients according to age and risk of recurrence of the AML.
Standard treatment of recurrent adult AML depends on the subtype of AML and may include combination chemotherapy, biologic therapy with monoclonal antibodies, stem cell transplantation or clinical trials.
In 1984, a study conducted by the Fred Hutchinson Cancer Research Center showed that nearly half of patients with AML who received bone marrow transplants after their first remission survived at least five years, compared to only one-fifth of those treated with chemotherapy only. That dramatic result now means that many AML patients undergo bone marrow or stem cell transplantation while they are in the first remission. With improved treatments for transplant complications, five-year survival rates for people with AML are as high as 70% (Fred Hutchinson Cancer Research Center website).
Clinical Trials
Risk Factors
The cause of AML is unknown. It is not contagious and is not inherited. Very rarely, AML may occur in unexpectedly high frequencies in certain families. Older people are more likely to develop the disease.
Several factors have been linked to increased risk of AML, including:
- exposure to very high doses of radiation
- exposure to benzene
- smoking
- exposure to chemotherapy
Genetic disorders such as Fanconi anemia and Down syndrome are associated with an increased risk of AML.
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