TEMPORAL TRENDS AND RELATIVE RISKS OF INTESTINAL AND EXTRA-INTESTINAL CANCERS IN PERSONS WITH INFLAMMATORY BOWEL DISEASES: A POPULATION-BASED STUDY FROM A LARGE CANADIAN PROVINCE

Background: Cancer is a major cause of morbidity and mortality in persons with inflammatory bowel disease (IBD). We evaluated temporal trends and relative risks of intestinal and extra-intestinal cancers among persons with IBD and matched controls.

Methods: Using population-level administrative data housed at IC/ES (Ontario, Canada), we identified persons with IBD (2002-2017) using a validated algorithm, which also identified diagnoses of Crohn's disease (CD) and ulcerative colitis (UC). Each case was age and sex matched to 10 non-IBD controls and all persons were followed to 2020 for the development of cancer, as identified in the Ontario cancer registry. Only the first organ-specific cancer was counted in each analysis, after which an individual was censored. Individuals were excluded in the analyses of colorectal cancers (CRC) if they underwent proctocolectomy before their first IBD contact and censored at the time of proctocolectomy thereafter. Individuals were censored in all analyses when they died or lost provincial health insurance coverage. Annual cancer incidence rates were age- and sex-standardized to the July 2015 Ontario IBD population. Log-transformed standardized incidence rates for each cancer were analyzed using linear regression, with a first-order autoregressive term, to derive the average annual percentage change (AAPC). Quasi-Poisson regression was used to calculate rate ratios between persons with IBD and controls (2017-2020).

Results: Of the 19,984,538 individuals in the Ontario population from 2002 to 2017, we identified 110,919 persons with IBD. Among persons with IBD, the AAPC significantly decreased for colorectal cancers (CRC) but significantly increased for small bowel cancers, non-Hodgkin’s lymphoma, melanoma and cervical cancers (Table 1). Rates of lung, breast and prostate cancers did not change in IBD, but declined significantly in controls. These trends were similar in persons with UC and matched controls (excluding small bowel cancers). Among persons with CD, the AAPC was not significant for any cancer. During 2017-2020, rates of intestinal cancers, lymphomas, biliary tract cancers and lung cancers were significantly higher in persons with IBD than controls, whereas they did not differ for melanoma or for breast, cervical or prostate cancer.

Conclusions: Rates of CRC have declined, whereas rates of small bowel cancers, NHL, melanoma and cervical cancers have risen, over the past 25 years among persons with IBD . Trends for small bowel, lung, breast, cervical and prostate cancer, as well as for NHL, are discrepant from persons without IBD. Rates of intestinal cancers, lymphomas, biliary tract cancers and lung cancers are higher in persons with IBD than those without IBD. These data should be used inform discussions regarding cancer risks between IBD patients and their practitioners.