Age-Related Survival Differences in Patients With Inflammatory Bowel Disease-Associated Colorectal Cancer: A Population-Based Cohort Study

Background: Reported outcomes for colorectal cancer associated with inflammatory bowel disease are inconsistent. We compared survival outcomes in colorectal cancer patients with and without inflammatory bowel disease using a population-based cohort and elicited prognostic factors associated with survival. Methods: Adult patients with a diagnosis of colorectal cancer in 2007-2015 were identified from the Ontario Cancer Registry. Those with inflammatory bowel disease (IBD) were detected via the validated Ontario Crohn's and Colitis Cohort. The primary outcome measure was overall survival from time of colorectal cancer diagnosis until the date of death. Secondary outcome measures included treatments received and publicly provided health care costs. Results: Colorectal cancer was diagnosed in 67,137, with inflammatory bowel disease present in 783 (1.2%). The IBD-associated colorectal cancer patients were younger at diagnosis (median range, 55-59 vs 70-74 years; P < 0.001). Five-year survival in IBD-associated patients was 56.4% (95% confidence interval [CI], 52.6%-59.9%) and 57.0% (95% CI, 56.6%-57.4%) in sporadic colorectal cancer (P = 0.8). Inflammatory bowel disease was a significant predictor of death (hazard ratio, 1.45; 95% CI, 1.29-1.63; P < 0.001) after adjusting for other variables. In patients under 50, 5-year survival was significantly (P < 0.001) reduced in the IBD population (56.8%; 95% CI, 49.4%-63.5%) compared with the sporadic colorectal cancer population (71.4%; 95% CI, 70.0%-72.7%). Similar results were observed in those 50-64 years old. Conclusions: Patients with IBD-associated CRC appear to have worse survival than those with sporadic CRC. In subgroups based on age, this difference appears to be driven by young (<65 years old) patients with IBD. These findings may direct future research on treatment for this high-risk population.