Rural-Urban Differences in Colon Cancer Risk in Blacks and Whites: The North Carolina Colon Cancer Study

Context: Geographic and racial variations in cancer incidence have been observed. Studies of colorectal carcinoma indicate a higher incidence and mortality rate for blacks than for whites in the United States. Purpose: We evaluated the effect of rural versus urban residence on colon cancer risk and stage of disease at diagnosis in blacks and whites. Methods: Interviews were conducted with 558 colon cancer cases and 952 controls enrolled in the North Carolina Colon Cancer Study, a population-based case-control study of blacks and whites residing in 33 contiguous counties. Findings: Residence in a rural area was associated with increased colon cancer risk (odds ratio, 1.4; 95% confidence interval, 1.1-1.8). This association was no longer significant after controlling for recent use of colorectal cancer screening tests (odds ratio, 1.2; 95% confidence interval, 0.9-1.6). Risk estimates were not modified by race nor were they markedly different for extent of disease at diagnosis. However, colorectal cancer screening rates were lower for blacks than for whites. Conclusion: Our findings suggest that rural blacks and whites are at increased risk of colon cancer regardless of stage of disease at diagnosis than their urban counterparts; this relationship may be mediated by screening behavior.