The cause of leukemia is not known, but the prevalence of leukemia is higher in people with the following risk factors than in the general population.
- Viral factors: People with HTLV-1 virus infection are at risk for developing adult T-cell leukemia/lymphoma.
- Chemical factors: The incidence of leukemia is higher in people exposed to benzene and its derivatives than in the general population. Leukemia has also been reported to be induced by nitrosamines, protamine and its derivatives, and chloramphenicol. Some antitumor cytotoxic drugs, such as nitrogen mustard, cyclophosphamide, methylbenzylhydrazine, VP16, and VM26, have leukemogenic effects, and some patients are prone to develop leukemia called “second tumors” 2 to 5 years after chemotherapy for the primary tumor.
- Radiological factors: There is evidence that various types of ionizing radiation can cause leukemia in humans. The development of leukemia depends on the dose of radiation absorbed by the body, and can be induced by moderate or high doses of radiation to the whole body or part of the torso. It is still uncertain whether small doses of radiation can cause leukemia. The incidence of leukemia is significantly increased in those who are frequently exposed to radioactive materials (e.g., cobalt-60). Diagnosis and treatment with high doses of radiation can result in an increased incidence of leukemia.
- Genetic factors: The incidence of leukemia is higher in people with chromosomal aberrations than in normal people.