The epidemiology of acute promyelocytic leukaemia

Recent progress has demonstrated that acute myelogenous leukaemia (AML) can be classified by chromosomal aberrations and leukaemia-specific molecular gene rearrangements into homogeneous biological subgroups. However, descriptive epidemiological reports on AML consider the disease as a single entity. Acute promyelocytic leukaemia (APL) is an example of a truly unique AML subtype that has an easy-to-recognize morphology associated uniformly with distinct chromosomal and gene rearrangement aberration. Thus, APL is amenable to epidemiological studies as a model of human AML with a specific and well-characterized chromosomal and molecular abnormality. This chapter shows that epidemiological characteristics of APL are different from those of non-APL AML using data from the Los Angeles tumour registry and other sources. The principal distinct APL epidemiological features that so far have been described are the constant incidence with age after age 20, equal incidence in males and females and higher frequency among patients originating in Latin America. The APL-specific PML/RAR alpha gene rearrangement is different in Latinos and non-Latinos. Therapy-related APL has the same response to treatment and outcome as de novo APL. It is therefore likely that aetiological factors for APL are different from those of other AML subtypes. So far no environmental and/or occupational risk factors have been found for APL. Future molecular studies of the APL-specific fusion gene combined with epidemiological and environmental investigations might lead to better understanding of specific aetiological factors in APL patients.