P777 The cancer incidence in paediatric onset inflammatory bowel disease: a population-based study from Denmark
M. Malham*1, C. Jakobsen1,2, A. Paerregaard1, L. B. Riis3, K-L. Kolho4, V. Wewer1
1Hvidovre University Hospital, The Paediatric Department, Hvidovre, Denmark, 2Hvidovre University Hospital, The GastroUnit, Hvidovre, Denmark, 3Herlev Hospital, The Department of Pathology, Herlev, Denmark, 4Tampere University Hospital, The Paediatric Department, Tampere, Finland
The incidence of colorectal cancer (CRC) in IBD has been the subject of much debate over the last decades and seems to have decreased to a negligible .However, in most studies sub-analysis revealed young age at diagnosis to be a risk factor for CRC. A recent study from Sweden  reported an increased risk of cancer (all types) in paediatric onset IBD (pIBD) but the reproducibility of this in other countries is unknown. In this population-based study we aimed to estimate the incidence of cancer in the Danish pIBD population in a 23 years period.
The pIBD population was defined as individuals registered in the Danish Patient Register (LPR) with a diagnosis of Crohn’s disease, ulcerative colitis or IBD-unclassified before their 18th birthday during the period 01 January 1992 to 31 December 2014. This cohort was cross referenced with the cancer register identifying all pIBD patients who subsequently developed cancer. Standardised incidence ratios (SIR) were calculated comparing observed numbers with expected numbers of cancers.
3.279 patients with pIBD were identified and followed through. Of these, 125 were registered in the cancer register. Using the Danish Pathology Register as gold standard, the cancer diagnosis could be confirmed in only 93 of these patients. The SIR of cancer in general was 4.6 (95% confidence interval (CI): 3.7-5.6). The cancer specific SIR was 7.2 (CI: 2.3–16.8) in CRC, 111 (CI: 41–243) in bile duct cancers, 3.6 (CI: 1.9–6.2) in skin cancers and 1.7 (CI: 0.5–4.3) in lymphoma.
Conclusion: In this population-based study, we found an increased risk of cancer in pIBD. By analysing the cancer specific SIR, we found a strikingly high increased risk of bile duct cancers in pIBD which consisted of cholangiocarcinomas only. These findings are in line with the existing Swedish study. However, the wide CI in our cancer specific analysis calls for larger international multi-centre studies.
1. Jess T Decreasing risk of colorectal cancer in patients with inflammatory bowel disease over 30 years. 2012.
2. Olén O et al. Childhood onset inflammatory bowel disease and risk of cancer: a Swedish nationwide cohort study 1964–2014.