Background & aims: Inflammatory bowel disease (IBD) is a risk factor for colorectal cancer (CRC). There have been marked changes in the management and treatment of IBD over the past decades, but little is known about how these changes have impacted morbidity and mortality (time trends in risk) of CRC in patients with IBD.
Methods: We assessed cancer occurrence and mortality in a large population-based cohort of patients with IBD who were diagnosed from 1954 to 1989 (n = 7607). Through register links, we collected data on vital status of all registered cases of CRC, as well as intestinal surgeries and mortalities from CRC through 2004. Relative risks for CRC incidence and mortality, by calendar period of follow-up evaluation, were assessed within the cohort (using Poisson regression and taking age, sex, extent of IBD, and time since IBD diagnosis into account) and also compared with the general population using standardized incidence and mortality ratios.
Results: During 198,227 person-years of follow-up evaluation for the 7607 patients with IBD, 188 new cases of CRC were observed (crude incidence, 95 per 100,000; 95% confidence interval, 82-109); 92 deaths from CRC were registered. Within the IBD cohort, as well as vs the general population, the incidence of CRC showed a tendency towards a decline whereas the mortality from CRC decreased several-fold from the 1960s through 2004.
Conclusions: Over the past 35 years, the risk of diagnosis of CRC in patients with IBD has not declined significantly, but the risk of dying of CRC has decreased substantially.