BACKGROUND: Recent studies report increased risks of both cancer and mortality in paediatric onset inflammatory bowel disease (pIBD) but the reproducibility of this is unknown.

AIM: To estimate the risk of cancer and mortality in the Danish and Finnish pIBD population in a 23-year period compared to the general population.

METHODS: The pIBD population was defined as individuals registered in the national patient registries with a diagnosis of Crohn's disease (CD), ulcerative colitis (UC) or IBD-unclassified before their 18th birthday from 1992 to 2014. This cohort was cross referenced with the national cancer and mortality registries identifying all pIBD patients who subsequently developed cancer and/ or died and followed up to the end of 2014. Risk estimates are presented as standardised incidence ratios calculated based on incidence figures from the populations.

RESULTS: Six thousand six hundred and eight-nine patients with pIBD were identified (median age at follow-up 22.3 years; median follow-up: 9.6 years [interquartile range: 4.8-16.0]). Seventy-two subsequently developed cancer and 65 died. The standardised incidence ratio of cancer in general was 2.6 (95% CI: 1.8-3.7) and 2.5 (95% CI: 1.8-3.4) in CD and UC, respectively. The standardised mortality ratios were 2.2 (95% CI: 1.4-3.4) and 3.7 (95% CI: 2.7-5.0) in CD and UC, respectively. The leading causes for mortality were cancer, suicide and infections.

CONCLUSIONS: We found an increased risk of cancer and mortality in pIBD. This underlines the importance of cancer surveillance programs and assessment of mental health in the standard of care in adolescent pIBD patients.