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

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.

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.

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.

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.