Colorectal cancer in an African city population in transition.

An enquiry has been made on a series of African patients with colorectal cancer who were admitted in 1995-1999 to Chris Hani Baragwanath Hospital (3200 beds), and who lived in Soweto (population about 1 million), Johannesburg, South Africa. In the urban context described, Africans have considerably more advantages, socio-economically, dietarily and in other respects, than their rural counterparts. The 126 patients comprised 58 males and 68 females, giving calculated incidence rates in their communities for colorectal cancer of 1.7 and 2.0, respectively, per 100,000 'world' population. In contrast, as indicated in the South African Cancer Registry for 1993-1995, the corresponding rates for white males and females were 24.7 and 19.3, respectively, per 100,000. The proportion of African patients under 40 years was 19.0%; but was only 4.0% in the white population. In contrast to this major disparity, there was only a minor interethnic disparity regarding cancers that are very common in Africans, namely, those of the oesophagus and lung. Hence, with ongoing transitional changes - in diet and other respects - the relatively high proportion of younger African patients probably indicates a rising occurrence of colorectal cancer in the urban African population.