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.