Who Is at Risk?

In many cases, no one knows why some people develop leukemia and others do not. However, scientists have identified some risk factors for the disease. A risk factor is anything that increases a person's chances of developing a disease.

Most people who have known risk factors do not get leukemia, while many who do get the disease have none of these risk factors.

Risk Factors

Studies have identified the following risk factors for leukemia: older, male, white, working with certain chemicals, smoking, exposure to very high levels of radiation, certain health conditions, and past treatment with chemotherapy or radiation therapy.

More than 65 percent of people diagnosed with leukemia are over 55. Leukemia occurs more often in men than women and is more common among white people than other races.

Exposure to Benzene

Chronic exposure to certain chemicals may lead to the development of leukemia. Benzene is a widely used chemical that has been linked to leukemia. The greatest risk of exposure to high concentrations of benzene is worksites such as chemical plants and gasoline-related industries. However, government agencies have regulated the amount of benzene exposure in the U.S. industry, so cases of leukemia linked to benzene now are rare in this country.

Benzene is usually found in low levels in the general environment. However, areas around gasoline stations, high vehicular traffic, and industrial sources may have higher levels. Benzene is also found in tobacco smoke. It is estimated that about half of the benzene exposure in the United States is from cigarette smoke. Smoking is a risk factor for leukemia.

Disorders and Genetic Diseases

Certain disorders and genetic diseases, such as Down syndrome, may increase the risk of leukemia. About 3 out of 10 people with a blood disorder known as myelodysplastic syndrome develop acute myeloid leukemia. In this disorder, as in leukemia, abnormal cells are formed in the bone marrow and too few healthy blood cells enter the bloodstream.

Radiation Exposure

People exposed to very high levels of radiation, such as the atomic bomb blast in Hiroshima, Japan or nuclear power plant accidents, also are at risk of developing leukemia. Studies of atomic blasts have estimated that survivors have a five and a half times greater risk of developing leukemia than the general public.

Cancer Treatments

Chemotherapy and radiation therapy have been helpful to a lot of people in the treatment of many forms of cancer, and indeed are often lifesaving. These therapies have been linked to the development of second cancers, including leukemia, many years after treatment. Chemotherapy for a first cancer is a stronger risk factor for developing leukemia later than is radiation therapy. The combination of chemotherapy and radiation can significantly increase the risk of leukemia after a first cancer.

Powerful cancer-fighting chemotherapy drugs, known as alkylating agents and epipodophyllotoxins, have been associated with leukemia. The dose given and length of treatment as well as other factors may contribute to a person's risk of developing leukemia. Acute myeloid leukemia is the most common type of cancer that has been linked to chemotherapy treatment.

Radiation therapy may increase a person's chance of developing leukemia. Several factors influence this risk, such as the dose of radiation administered. A person's age at the time of therapy does not seem to be a risk factor for leukemia.

Recently, researchers have gained a much greater understanding of the risk of second cancers due to earlier treatment exposures. They have been able to limit the effective doses given in primary cases so as to reduce the risk of a recurrence or second cancer.