Risk of malignancy in patients with inflammatory bowel disease: A population‐based cohort study from China

Carcinogenesis is one of the major complications for patients with inflammatory bowel disease (IBD) and causes poor prognosis. We aimed to describe cancer incidence in the Chinese IBD cohort compared to general population-based cancer registration data and further explore associated risk factors for cancer occurrence in IBD patients. IBD inpatients from January 1998 to January 2018 in Peking Union Medical College Hospital (PUMCH) were included in our study. Patients were followed-up from the date of IBD diagnosis until either the date of first cancer diagnosis or January 2019. Standardized incidence ratios (SIRs) of overall cancer and site-specific cancers were calculated. A total of 869 Ulcerative Colitis (UC) and 516 Crohn's disease (CD) patients were finally included with median follow-up time of 7 and 5 years, respectively. Fifty-three cases developed malignancies. After standardization by age and gender, SIR of total cancer occurrence in IBD patients was 1.77 (95% CI, 1.33-2.32). As for UC, digestive cancers (SIR 3.75; 95% CI, 2.29-5.80), thyroid cancer (SIR 10.34; 95% CI, 4.72-19.64) and hematological malignancies (SIR 6.25; 95% CI, 1.68-16.00) had the highest incidence, which were prominent in young and middle-aged patients. Use of steroids, immunosuppressants or infliximab did not present higher risk of malignancies in UC patients. There was no significant difference in cancer risk between CD patients and general population. In conclusion, the increased risks of multiple cancers are particularly prominent in Chinese UC patients and these findings can provide more targeted guidance for cancer monitoring in Chinese IBD patients.