Epidemiology of acute leukaemia in the Cape Province of South Africa

Of 535 consecutive cases of acute leukaemia diagnosed in the Cape Province between 1978 and 1985, demographic data are incomplete in 75 black patients and they have had to be excluded from the spatial analysis. Of the remaining 460 cases, 223 (48.5%) occurred in white patients and 237 (51.5%) in those of mixed ancestry, classified as coloureds according to the Population Registration Act No. 30 of 1950. The average incidence was 2.12, 1.37 and 0.58/100 000 for whites, coloureds and blacks respectively. There was no temporal trend in the incidence of acute leukaemia between the three race groups. The median age for whites was 30 years and for the coloureds was 15 years, which is comparable to the 16 years for the black patients. The two-peak age distribution for leukaemia was seen in the white group, but was absent in the other two groups. This is accounted for by a different distribution in non-lymphoblastic as opposed to lymphoblastic subtypes. Furthermore, there was a disproportionately high frequency of acute progranulocytic leukaemia in the black patients, whereas the white and coloured groups were similar. There was a single, clearly defined macro-scale cluster restricted to white patients in Statistical Region 17 (SR-17). This exploratory study provides the first epidemiologic data for acute leukaemia in the Cape Province. It needs to be extended in order to verify these observations under more controlled circumstances and to seek evidence for some environmental factors that may account for the geographical cluster.