Rural-urban differences in the long-term risk of colorectal cancer after adenoma removal: a population-based study.

Background: We investigated the impact of municipality of residence on colonoscopic surveillance and colorectal cancer risk after adenoma resection in a French well-defined administrative area.

Methods: This registry-based study included all patients residing in Côte d'Or (n=5769) first diagnosed with colorectal adenomas between January 1, 1990, and December 31, 1999. Information about colonoscopic surveillance and colorectal cancer incidence was collected until December 31, 2003.

Results: A rural place of residence reduced the probability of colonoscopic surveillance in men [HR=0.89 (95%CI: 0.79-0.99), p=0.041] and in patients without family history of colorectal cancer [HR=0.91(0.82-0.99), p=0.044]. After a median follow-up of 7.7 years, 87 patients developed invasive colorectal cancer. After advanced adenoma removal, the standardized incidence ratio for colorectal cancer was 3.03 (95%CI: 1.92-4.54) for rural patients and 1.87 (95%CI: 1.26-2.66) for urban patients compared with the general population. The risk of colorectal cancer was higher in rural patients than in urban ones only after removal of the initial advanced adenoma [HR=1.73 (95%CI: 1.01-3.00, p=0.048)]. Further adjustment for surveillance colonoscopy, physician location, and other confounders had little impact on these results.

Conclusion: The increased risk of subsequent colorectal cancer after advanced adenoma removal in French rural patients was not explained by a lower rate of colonoscopic surveillance. The role of socio-economic and environmental factors requires further exploration.