Objectives: We aimed to determine if use of 5-aminosalicylates (5-ASA) was associated with a reduced risk of colorectal cancer (CRC) in people with inflammatory bowel disease (IBD).
Methods: We used the population-based University of Manitoba IBD Epidemiology Database that tracks all health-care visits from 1984 to 2008 of all Manitobans with IBD and all prescription medication use since 1995. In 2008, there were 8,744 subjects with IBD (ulcerative colitis 4,325, Crohn's disease 4,419, females 4,851, males 3,893). In study I, we assessed the incidence of CRC among 5-ASA users (≥1 year, ≥5 years of cumulative use) compared with nonusers. In study II, we assessed a cohort of those with CRC (n=101) diagnosed in 1995-2008, matched to a control cohort by age, sex, disease duration, and disease diagnosis without CRC (n=303), and logistic analysis was undertaken.
Results: For study I, the hazard ratio for CRC among 5-ASA users was 1.04 (95% confidence interval (CI) 0.67-1.62, P=0.87) at ≥1 year of use and 2.01 (95% CI 1.04-3.9, P=0.038) at ≥ 5 years of use with no difference when assessing by diagnosis. Males, but not females, using 5-ASA for ≥ 5 years had an increased risk of CRC. In study II, CRC cases had similar use of any 5-ASA compared with controls for ≥ 1 year of use (1.02, 95% CI 0.60-1.74) or ≥ 5 years (1.96, 95% CI 0.84-4.55), and a similar mean number of 5-ASA prescriptions at 10 vs. 11 (P=0.8) and a similar mean number of dose days at 330 vs. 410 (P=0.69).
Conclusions: Our results support the majority of studies to date that 5-ASA is not chemoprophylactic in IBD for CRC.