Most people with leukemia experience no risk factors. Although the specific cause of leukemia is not known, scientists suspect viral, genetic, environmental or immunologic factors may be involved. These include:
Viruses: Some viruses cause leukemia in animals; but, in humans, viruses cause only one rare type of leukemia. Even if a virus is involved, leukemia is not contagious. It cannot spread from one person to another. There is no increased occurrence of leukemia among friends, family and caregivers who have close contact with leukemia patients.
Inherited disorders: Rarely, genetic changes that may increase chances of developing leukemia run in families.
Environmental factors: High-dose radiation and exposure to certain toxic chemicals have been directly related to leukemia. But, this has been true only in extreme cases, such as atomic bomb survivors in Nagasaki and Hiroshima or industrial workers exposed to benzene. Exposure to ordinary X-rays, like chest X-rays, is not believed to cause leukemia.
Immune system deficiencies: These appear to put people at greater risk for cancer because of the body's decreased ability to resist foreign cells. There is evidence that patients treated for other types of cancer with some types of chemotherapy and/or high-dose radiation therapy may later develop leukemia.
These factors may play a part in a small percentage of leukemia cases. Yet, for most patients, the cause of leukemia is unknown. Not everyone with risk factors develops leukemia. However, if you have risk factors, it's a good idea to discuss them with your doctor.