The long-term incidence of dysplasia and colorectal cancer in a Crohn's colitis population-based cohort.

Aim: The risk of developing colorectal cancer (CRC) in Crohn's disease (CD) has been variably reported. Chronic inflammation is associated with an increased risk of neoplasia; variable outcomes in CD possibly reflect the heterogeneous nature of the disease. The aim of this work was to characterize the risk of CRC in a New Zealand population-based cohort of CD patients with colonic inflammation.

Method: A review of all participants with CD in the population-based Canterbury Inflammatory Bowel Disease Study was conducted. Data on demographics, endoscopic surveillance, presence of dysplasia/neoplasia and oncological outcome were extracted. The age-adjusted standardized incidence ratio (SIR) was used to compare the incidence of CRC in the cohort with the incidence of CRC in the New Zealand population in 2006.

Results: Data on 649 patients with CD were collected. Four hundred and thirty-six participants (58% female) with ileocolonic or colonic CD were included for analysis. CRC was diagnosed in 13 patients (62% female). The median age at CRC diagnosis was 58.5 years, and the mean duration of CD prior to diagnosis of CRC was 20.4 years. When compared with the New Zealand population (using census data), the overall age-adjusted SIR was 4.1 (95% CI 2.4-7.1).

Conclusion: This population-based cohort of patients with colonic CD shows a significantly increased risk of CRC compared with the general population. This is consistent with the colonic location of inflammation increasing the risk of neoplasia. Inclusion of patients with isolated upper gastrointestinal/ileal CD in similar studies may mask the truly increased risk for patients with long-standing colonic inflammation.