DOP44 Cancer risk in a high-incidence inflammatory bowel disease population: a Faroese IBD cohort study

Abstract Background The association between inflammatory bowel disease and malignancy is still controversial despite many observational studies. The Faroese population exhibits the highest occurrence of inflammatory bowel disease (IBD) in the world. The aim of this study was to investigate the risk of cancer in Faroese IBD patients within the nationwide Faroese IBD cohort. Methods This was a nationwide cohort study of all IBD patients diagnosed in the Faroe Islands from 1960 to 2014. Clinical demographics and cancer diagnosis were retrieved from patient files and from the Faroese cancer registry. Patients were followed until the event of cancer, death or emigration. Patients diagnosed with cancer prior to the IBD diagnosis were excluded. Observed numbers of cancer were compared with expected numbers based on ASR(N) (Nordic age- and sex-specific incidence rates) from Nordcan, by multiplying ASR(N) with person-years and follow-up in the study cohort and presented as standardised incidence ratios (SIRs) with 95 % intervals (CIs). Results The cohort consisted of 664 incidence IBD patients. After excluding 12 patients with cancer prior to IBD diagnosis, 652 patients with a total follow-up length of 11 476 person-years were included (414 UC with 7.494 patient-years, 128 IBDU with 2.038 patient-years and 110 CD with 1.944 patient-years). A total of 56 patients developed cancer during the follow-up period compared with 39.2 expected cases in the background population. We observed no gender difference. In UC, 33 observed compared with 25.7 expected patients developed cancer (SIR 1.28; 95% CI, 0.88–1.80). In IBDU, 13 observed compared with 6.9 expected patients developed cancer (SIR 1.88; 95% CI 1.00–0.22). In CD, 10 cases were observed compared with 6.6 expected (SIR 1.51; 95% CI 0.73–2.79). The most common types of cancers observed are shown in Table 1. Conclusion In this nationwide cohort study, we found no overall risk of cancer in IBD patients in the geographic isolated Faroe Island. However, skin cancer occurred more than expected in IBDU patients. This finding needs to be investigated further including the influence of treatment on cancer risk.