Subsite distribution of large bowel cancers among the ethnic and dialect groups in Singapore.

The subsite distribution of large bowel cancers among the major ethnic groups and among major Chinese dialect groups in Singapore were analysed. It was found that the overall pattern of subsite distribution of large bowel cancers was remarkably similar among the sexes, ethnic and dialect groups. There was a progressive increase in the proportion of cancers from the right to the left side of the large bowel except for a decrease in the descending colon. The similarity in the pattern of subsite distribution despite differences in risk suggested that some common pathogenetic mechanism might be operative. It is consistent with the concept of effective exposure of the intestinal mucosa to carcinogens. The finding that greater proportions of sigmoid and rectal cancers occurred among the older age groups gave further support to such a concept. The findings of this study however do not exclude the possibility of subsite differences in sensitivity and response to carcinogens.