Background: Recently reported risks of colorectal cancer (CRC) in inflammatory bowel disease (IBD) have been lower than those reported before 2000. The aim of this meta-analysis was to update the CRC risk of ulcerative and Crohn's colitis, investigate time trends, and identify high-risk modifiers.
Methods: The MEDLINE search engine was used to identify all published cohort studies on CRC risk in IBD. Publications were critically appraised for study population, Crohn's disease localization, censoring for colectomy, and patient inclusion methods. The following data were extracted: total and stratified person-years at risk, number of observed CRC, number of expected CRC in background population, time period of inclusion, and geographical location. Pooled standardized incidence ratios and cumulative risks for 10-year disease intervals were calculated. Results were corrected for colectomy and isolated small bowel Crohn's disease.
Results: The pooled standardized incidence ratio of CRC in all patients with IBD in population-based studies was 1.7 (95% confidence interval [CI], 1.2-2.2 ). High-risk groups were patients with extensive colitis and an IBD diagnosis before age 30 with standardized incidence ratios of 6.4 (95% confidence interval, 2.4-17.5) and 7.2 (95% confidence interval, 2.9-17.8), respectively. Cumulative risks of CRC were 1%, 2%, and 5% after 10, 20, and >20 years of disease duration, respectively.
Conclusions: The risk of CRC is increased in patients with IBD but not as high as previously reported and not in all patients. This decline could be the result of aged cohorts. The risk of CRC is significantly higher in patients with longer disease duration, extensive disease, and IBD diagnosis at young age.