What are the risk factors for acute lymphocytic leukemia?

A risk factor is something that affects your chance of getting a disease such as cancer. Some risk factors, like smoking, can be controlled. Others, like a person's age or family history, can't be changed.

But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will definitely get the disease. And many people who get the disease may have few or no known risk factors. Even if a person has one or more risk factors and develops cancer, it is often very hard to know how much they might have contributed to the cancer.

There are only a few known risk factors for acute lymphocytic leukemia (ALL).

Radiation exposure

Exposure to high levels of radiation is a risk factor for both ALL and acute myeloid leukemia (AML). Japanese atomic bomb survivors had a greatly increased risk of developing acute leukemia, usually within 6 to 8 years after exposure.

The possible risks of leukemia from exposure to lower levels of radiation, such as from radiation therapy or from medical imaging tests (such as x-rays) are not well-known. Exposure of a fetus to radiation within the first months of development may carry an increased risk of leukemia, but the extent of the risk is not clear.

If there is an increased risk from lower levels of radiation it is likely to be small, but to be safe, most doctors try to limit a person's exposure to radiation as much as possible.

Certain chemical exposures

The risk of ALL may be increased by exposure to certain chemotherapy drugs and certain chemicals, including benzene. Benzene is a solvent used in the rubber industry, oil refineries, chemical plants, shoe manufacturing, and gasoline-related industries, and is also present in cigarette smoke, as well as some glues, cleaning products, detergents, art supplies, and paint strippers. Chemical exposure is more strongly linked to an increased risk of AML than to ALL.

Certain viral infections

Infection with the human T-cell lymphoma/leukemia virus-1 (HTLV-1) can cause a rare type of T-cell acute lymphocytic leukemia. Most cases occur in Japan and the Caribbean area. This disease is not common in the United States.

Epstein-Barr virus (EBV) most often causes infectious mononucleosis ("mono") in the United States. In Africa, the virus has been linked to Burkitt lymphoma, as well as to a form of acute lymphocytic leukemia.

Inherited syndromes

Acute lymphocytic leukemia does not appear to be an inherited disease. It does not seem to run in families, so a person's risk is not increased if a family member has the disease. But there are some inherited syndromes with genetic changes that seem to raise the risk of ALL. These include:

• Down syndrome
• Klinefelter syndrome
• Fanconi anemia
• Bloom syndrome
• Ataxia-telangiectasia
• Neurofibromatosis

Race/ethnicity

ALL is more common in whites than in African Americans, but the reasons for this are not clear.

Gender

ALL is slightly more common in males than in females. The reason for this is unknown.

Having an identical twin with ALL

This risk is largely confined to the first year of life. As mentioned earlier, most cases of ALL are not thought to have a strong genetic link. Many doctors feel the increased risk among identical twins may be due to leukemia cells being passed from one fetus to the other while still in the womb.

Uncertain, unproven or controversial risk factors

Other factors that have been studied for a possible link to ALL include:

• Exposure to electromagnetic fields (such as living near power lines or using cell phones)
• Workplace exposure to diesel, gasoline, pesticides, and certain other chemicals
• Smoking
• Exposure to hair dyes

So far, none of these factors has been linked conclusively to ALL. Research in these areas continues.