Background: Patients with inflammatory bowel disease (IBD) are at increased risk of colorectal cancer (CRC). Recently, new phenotypes of CRC in IBD have been suggested. Studies of the prognosis of CRC in IBD have shown conflicting results. The aim of the study was to analyze factors for prognosis in CRC-IBD, including the impact of the new phenotypes.
Methods: By using the nationwide, population-based Cancer Registry of Norway, we compared survival of a CRC-IBD cohort with CRC in the background population (all-CRC), adjusting for the topographical distribution of dysplasia at cancer diagnosis (widespread versus localized neoplasia in IBD) and other factors. We also analyzed prognostic factors within CRC-IBD.
Results: The mean age at CRC diagnosis was 43 years in widespread, 52 years in localized neoplasia IBD, and 70 years in all-CRC (P < 0.05). Adjusted for cofactors, prognosis of CRC-IBD was poorer compared to all-CRC (mortality rate ratio [MRR] 3.71, 95% confidence interval [CI]: 2.54-5.42, P < 0.001). Prognosis of widespread neoplasia IBD was poorer compared to all-CRC (MRR 4.27, 95% CI: 2.83-6.44, P < 0.001) and compared to localized neoplasia IBD (MRR 3.58, 95% CI: 0.87-14.72, P = 0.076). Survival was not significantly different between localized neoplasia IBD and all-CRC (P = 0.132).
Conclusions: The results demonstrate lower age and poorer survival of CRC in IBD compared to CRC in the background population. The unfavorable effect of IBD on prognosis of CRC was pronounced in widespread neoplasia IBD. The diagnosis of this phenotype seems to be an important prognostic sign in patients with CRC in IBD.