Risk of intestinal and extra-intestinal cancers in patients with inflammatory bowel diseases: A population-based cohort study in northeastern Italy

The cancer risk of patients with inflammatory bowel diseases (IBD) has not been well documented in southern Europe. This study aimed to evaluate the overall pattern of cancer risk among patients with IBD in Friuli Venezia Giulia, northeastern Italy. A population-based cohort study was performed through a record linkage between local healthcare databases and the cancer registry (1995-2013). We identified 3664 IBD patients aged 18-84 years, including 2358 with ulcerative colitis (UC) and 1306 with Crohn's disease (CD). Sex- and age-standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were used to compare the cancer incidence of IBD patients with the general population. The cumulative cancer risk among IBD patients reached about 10% after 10 years of follow-up. A total of 246 cancers occurred among UC patients (SIR = 1.05, 95% CI: 0.92-1.19), and 141 among CD patients (SIR = 1.20, 95% CI: 1.01-1.41). As compared with the general population, no increased risk of colorectal cancers was observed for either UC or CD patients, whereas the risk of anal cancer was significantly elevated among UC patients (SIR = 6.03, 95% CI: 1.24-17.60). Increased risks were seen for specific extra-intestinal cancers, including corpus uteri (SIR = 2.67, 95% CI: 1.07-5.50) and kidney (SIR = 2.06, 95% CI: 1.03-3.69) among UC patients; thyroid (SIR = 5.58, 95% CI: 2.41-11.00) and skin non-melanoma (SIR = 1.86, 95% CI: 1.32-2.55) among CD patients. This population-based study showed that both UC and CD patients had a colorectal cancer risk similar to that of the general population. However, they were at a higher risk of developing certain extra-intestinal cancer types. Although detection biases cannot be excluded, the study findings pointed to a role of long-standing exposures to immunosuppressive therapies, underlying disease status, as well as the interactions with lifestyle factors. Our findings lent additional support to the need for monitoring the cancer burden in this at-risk population.