Leukemia

Abstract

Leukemias represent 3% of all cancers in the world with relatively little variation between regions or countries. In many countries, leukemias are the most common cancer in children under 15, accounting for one third of all new cases. Cancer registries record leukemias under seven rubrics: acute lymphocytic (ALL), chronic lymphocytic (CLL), acute myeloid (AML), chronic myeloid (CML), monocytic (ML), other leukemias, and unspecified. The accuracy and the use of this classification varies from country to country, thus making comparisons difficult. With this in mind, the most striking features of the descriptive epidemiology are the low rates for CLL in China, Japan, and India and the apparent high risk for AML among the populations in the Pacific Islands. Age is strongly associated with leukemia type, ALL being a disease of childhood and CLL a disease of the elderly. The age distribution among children under 15 shows a peak between the ages of 2 and 4 years, which is more pronounced among whites than among blacks. Blacks in the US show lower rates than whites, and African children seem to have very low rates with no evidence of a peak between the ages of 2 and 4. Almost universally, males are more affected than females with a ratio of 2:1.