A risk factor is something that affects your chance of getting a disease, such as cancer. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for a number of cancers.
But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you definitely will get the disease. And many people who get the disease may not have had any known risk factors. Even if a person has a risk factor and develops cancer, it is often very hard to know how much that risk factor may have contributed to the cancer.
There are a few known risk factors for acute myeloid leukemia (AML).
Smoking
The only proven lifestyle-related risk factor for AML is smoking. Many people know that smoking is linked to cancers of the lungs, mouth, throat, and larynx (voice box), but few realize that it can also affect cells that don't come into direct contact with smoke. Cancer-causing substances in tobacco smoke are absorbed by the lungs and spread through the bloodstream to many parts of the body.
Certain chemical exposures
The risk of AML may be increased by exposure to certain chemicals. Long-term exposure to high levels of benzene is a risk factor for AML. 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, and some glues, cleaning products, detergents, art supplies, and paint strippers.
Some studies have linked heavy workplace formaldehyde exposure to AML risk, but this link was not seen in other studies.
Patients with other cancers who are treated with certain chemotherapy drugs are more likely to develop AML. Some of the drugs linked with these secondary (treatment-related) leukemias include mechlorethamine, procarbazine, chlorambucil, melphalan, etoposide, teniposide and cyclophosphamide. Combining these drugs with radiation therapy further increases the risk.
Most secondary cases of AML occur within 10 years after treatment of Hodgkin disease, non-Hodgkin lymphoma, or childhood acute lymphocytic leukemia (ALL). Secondary leukemias also sometimes occur after treatment of breast, ovarian, or other cancers.
Radiation exposure
High-dose radiation exposure (such as being a survivor of an atomic bomb blast or nuclear reactor accident) increases the risk of developing 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, x-rays, or CT scans, are not well-defined. If a fetus is exposed to radiation within the first months of development, it may carry an increased risk of leukemia, but the extent of the risk is not clear. If there is an increased risk 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 blood disorders
Patients with certain blood disorders seem to be at increased risk for getting AML. These include chronic myeloproliferative disorders such as polycythemia vera, essential thrombocytopenia, and idiopathic myelofibrosis. Chronic myelogenous leukemia (CML) is another type of myeloproliferative disorder, and some patients with CML later develop a form of AML. The risk of developing AML is increased further if treatment for these disorders includes some types of chemotherapy or radiation.
Some patients who have a myelodysplastic syndrome (a pre-leukemic condition) may develop AML. These conditions cause defects in blood cell formation, and over a period of years may evolve into leukemia. Patients who have a myelodysplastic syndrome and develop AML typically have a poor prognosis.
Congenital syndromes (present at birth)
For the most part, acute myeloid leukemia does not appear to be an inherited disease. It is rare for it to run in families, so a person's risk is not usually increased if a family member has the disease. But there are some congenital syndromes with genetic changes that seem to raise the risk of AML. These include:
- Down syndrome
- Fanconi anemia
- Bloom syndrome
- Ataxia-telangiectasia
- Blackfan-Diamond syndrome
Having an identical twin with AML
This risk is largely confined to the first year of life. As mentioned above, most cases of AML 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.
Gender
AML is more common in males than in females, but the reasons for this are not clear.
Uncertain, unproven or controversial risk factors
Other factors that have been studied for a possible link to AML include:
- Exposure to electromagnetic fields (such as living near power lines)
- Workplace exposure to diesel, gasoline, and certain other chemicals and solvents
- Exposure to herbicides or pesticides
So far, none of these factors has been linked conclusively to AML. Research in these areas is ongoing.
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