Racial differences in the incidence of colorectal cancer

Colon cancer is one of the most common cancers and the second most common cause of cancer mortality in Western societies. Population screening has been introduced as a means to reducing its impact; however, there are little or no data on the incidence of this disorder in the different populations that comprise the Canadian population.

To retrospectively determine the incidence of colorectal cancer in selected racial populations of British Columbia.

The British Columbia Cancer Agency database was used to retrieve information on the incidence of cancers occurring during the years 1994 to 1998, with the British Columbia and national population censuses used to derive the age-specific and age-standardized incidence rates of colorectal cancers. Surnames were used to identify the origin of individuals from South Asian and Chinese backgrounds.

For the Caucasian Canadian (C) population, the weighted age-standardized incidence rate ranged from 51.99 per 100,000 in 1995, to 57.68 per 100,000 in 1998. For Chinese Canadians (CC), the range was 39.2 per 100,000 in 1996, to 31.2 per 100,000 in 1998. For South Asian Canadians (SAC), the range was 7.40 per 100,000 in 1994, to 24.85 per 100,000 in 1998. The RR for the development of cancer were significantly different when comparing C versus CC (RR 1.9; 95% CI 1.58 to 2.31; P<0.001), C versus SAC (RR 7.1; 95% CI 4.20 to 12.0; P<0.0001) and CC versus SAC (RR 3.7; 95% CI 2.14 to 6.5; P<0.0001).

Significant differences in the incidence of colorectal cancers have been defined for the first time in various racial subgroups in British Columbia. This finding may have important implications for both screening and understanding of the environmental factors influencing the biology of these lesions. Because SAC have among the highest incidence of atherosclerotic heart disease and diabetes, it suggests that unidentified genetic and/or environmental protective factors are capable of countering the traditionally recognized risk of high saturated fat intake for the development of colorectal cancer.