Polyps and colorectal cancer in South African Blacks.

This study reflects the fact that cancer of the large bowel is uncommon in South African Blacks, and that colorectal polyps do not appear to constitute a precursor to most colorectal cancers. Furthermore, it is shown that dietary factors associated with this cancer in Western populations are not evident in the Black population. In the South African White population, however, the disease behaves in a similar way to that observed in Western countries. Other definitive differences found were the absence of multiple synchronous cancers and diverticular disease in the Blacks with colorectal cancer. It is thus postulated that dietary factors are absent, or have not been present for a sufficient length of time to influence the development of polyps or polyp--cancer sequence in this population. It is also possible that the adenoma--carcinoma progression observed in Western countries may not be relevant to the development of all colorectal carcinomas in communities such as those reported here.