Colorectal Cancer in Childhood‐onset Inflammatory Bowel Disease

Through linkage of data from Danish and Swedish national registers we identified 6937 patients with childhood (<18 years)‐onset Crohn disease (CD), 8514 patients with childhood‐onset ulcerative colitis (UC) and up to 10 times as many matched (sex, age, residence) reference individuals 1969–2017. During follow‐up to a median age of 27 (interquartile range = 21–39) years, 25 (0.36%) CD patients were diagnosed with colorectal cancer (CRC) versus 43 (0.06%) reference individuals, and 113 (1.33%) UC patients versus 45 (0.05%) reference individuals. The hazard ratio (HR) for CRC was 6.46 (95% CI = 3.95–10.6) in CD and 32.5 (95% CI = 23.0–45.9) in UC and increased with decreasing age at diagnosis. The HR for CRC was increased for all phenotypes, but with higher estimates for colonic CD [17.9 (95% CI = 7.43–43.3)] and UC with extensive/pancolitis [36.3 (95% CI = 22.8–57.8)]. The relative risk of CRC was increased for all phenotypes of childhood‐onset inflammatory bowel disease. Age at onset may be considered an additional risk factor when implementing surveillance programs.