Eleven sites of cancer in black gold miners from Southern Africa: a geographic enquiry.

The 5-year study of cancer in black gold miners, 1964-68, previously reported (Robertson et al., 1971) has now been extended for a separate 8-year period, 1972-79. This allows analyses of all cancers together and of 6 less common sites of cancer severally: lymphosarcomas, colon and rectum, leukaemia, stomach, pancreas and buccal cavity and also of those too rare to classify. The malignancies are considered by territory of origin of the gold miners. Lesotho miners have significantly fewer (P less than 0.05) tumours of the lymphatic and haemopoietic tissues and Natal miners have the highest incidence rates for 5 of the 6 sites (excluding leukaemia). A simple grouping method is applied to determine which of the 11 sites of cancer in the miners have similar distributions in their 10 territories of origin. The aetiological implications of clusters over space of certain sites of cancer are discussed. Finally, temporal change over the years 1964-79 shows a significant decrease overall (P less than 0.01) in cases of lymphosarcomas and colo-rectal cancers and an increase (P less than 0.05) in stomach cancer. The rare tumour, Kaposi's sarcoma, has also decreased significantly between the 2 periods studied.