Risk of malignancy in a high-incidence population-based cohort of Faroese patients with inflammatory bowel disease from 1960 to 2020 - a Faroese IBD cohort study.

Background: The association between inflammatory bowel disease (IBD) and malignancy remains disputed despite many observational studies. The Faroese population exhibits the highest occurrence of IBD in the world. This study aimed to investigate the cancer risk in Faroese IBD patients in a nationwide IBD cohort.

Methods: This study included all IBD patients diagnosed in the Faroe Islands between 1960 and 2020. Clinical demographics and cancer diagnoses were retrieved from patient files and the Faroese cancer registry. Cancer risk in IBD patients was calculated as standardized incidence ratios (SIRs) based on the Faroese background population's age- and sex-specific cancer incidence rates, retrievable from NORDCAN.

Results: The cohort consisted of 699 patients with a total follow-up time of 9,629 person-years. Overall, the risk of cancer was not statistically significantly increased compared to the background population. Patients diagnosed with cancer at age 50-59 years had higher overall cancer risk (SIR 1.8; 95% CI, 1.02-2.99) as did UC patients diagnosed with IBD at 50-59 (SIR 2.1; 95% CI, 1.10-3.54). Absolute numbers were small and no estimates for site-specific cancers reached statistical significance, though lung, breast, and cancer of the female reproductive organs were elevated among IBD and UC patients, and colorectal cancer in CD patients.

Conclusions: This nationwide study found no statistically significantly increased risk of cancer among Faroese patients with CD or UC, except from age 50 to 59 years. While the incidence of IBD is significantly higher in the Faroe Islands than in other countries, risk estimates of cancers are comparable.