|
Age: Approximately 60-70% of leukemia cases occur in individuals who are older than 50. The most common form of leukemia among children under 19 years of age is ALL. The incidence of ALL among one to four-year-old children is more than 9 times greater than the rate for young adults ages 20-24. Gender: Incidence rates for all types of leukemia are higher among males than among females. Males account for more than 56% of the cases of leukemia. This may be hormonally related. Radiation exposure: The risk of chronic myelogenous leukemia (CML) is increased among individuals who have been exposed to high doses of radiation. Radiation damages bone cells and may cause cancerous cells to develop. Atomic bomb survivors in Japan, those who lived near the nuclear reactor accident in Chernobyl, and armed forces who participated in American nuclear detonations during the late 1950s are examples of groups exposed to high levels of radiation. It is important to note, however, that standard diagnostic X-rays pose little or no increase in leukemia risk. Chemicals: The risk for acute leukemia is increased 20 times among workers with long-term exposure to benzene. Risk also is increased among workers exposed to some other solvents, herbicides, and pesticides. Agricultural chemicals, in particular, have been linked with an increased risk of chronic lymphocytic leukemia (CLL). In addition, some reports suggest that leukemia risk may be increased in workers in factories exposed to dioxin, styrenes, butadienes, or ethylene oxides. Viruses: The human T-cell leukemia virus I (HTLV-I) is related to acute T-cell leukemia. This type of leukemia is well documented in parts of the Caribbean and Asia, but it is uncommon in the United States and Europe. Higher rates of leukemia have also been reported in workers who are exposed to animal viruses, such as butchers, slaughterhouse workers, and veterinarians. Genetics: Studies have reported that in some types of leukemia, such as AML, genetics also may play a role in the risk for recurrence of the disease. Leukemia risk is increased 15 times among children with Down's syndrome, which is a genetically linked chromosomal abnormality (usually an extra copy of chromosome 21). Three rare inherited disorders, including Fanconi's anemia, Bloom's syndrome, and ataxia telangiectasia, also have an increased risk for leukemia. Race: Leukemia varies among racial and ethnic groups with different genetic make-ups. For example, rates of lymphoma and leukemia, such as chronic lymphocytic leukemia (CLL), are especially high in some Jewish populations, whereas Asian populations rarely develop CLL. First-degree relatives, including parents, children, and siblings of CLL patients, have two to four times the risk for leukemia due to genetics. Leukemia is one of the top 15 most frequently occurring cancers in minority groups. Cigarette smoking: Cigarette smoking is a known lifestyle-related risk factor for leukemia. Potential leukemia-causing chemicals in tobacco smoke include benzene, polonium-210, and polycyclic aromatic hydrocarbons (PAHs). These carcinogens (cancer-causing substances) are absorbed by the lungs and are spread via the bloodstream. It is estimated that one in four cases of acute myelogenous leukemia (AML) is the result of cigarette smoking. Cancer therapy: Individuals who have received chemotherapy and radiation therapy for previous cancers have a slightly greater chance of getting secondary leukemia (leukemia that arises after therapy). Acute myelogenous leukemia (AML) has been reported after chemotherapy and/or radiotherapy for various solid tumors (such as breast cancer and ovarian cancer), blood malignancies, and non-malignant conditions. The chemotherapeutic agents most often associated with secondary leukemias are procarbazine, chlorambucil, etoposide, mechlorethamine, teniposide, and cyclophosphamide. The risk is increased when these drugs are combined with radiation therapy. Many secondary leukemias are AMLs that develop within nine years after treatment of Hodgkin's disease, non-Hodgkin's lymphoma, or childhood CLL. Further chemotherapy often is ineffective in patients with secondary AML. Their prognosis is less favorable than that of typical AML patients. Other causes: The use of the antibiotic chloramphenicol has been linked with the development of childhood leukemia. Chloramphenicol is rarely used today. Other medications, such as growth hormones and phenylbutazone, also have reportedly shown some associations with leukemia. Leukemias and lymphomas have been observed in recipients of organ transplants, and certain immunodeficiency syndromes are associated with leukemias.
 |
Learn
