Cancer Risk in the Early Stages of Inflammatory Bowel Disease in Korean Patients: A Nationwide Population-based Study

Background and Aims: The association between inflammatory bowel disease [IBD] and cancer remains poorly defined in Asian populations. Therefore, we conducted a nationwide population-based study to determine the cancer risk in Korean patients with IBD. Methods: Using the National Health Insurance claims data, we collected data on patients diagnosed with IBD ( 5595 Crohn's disease [CD] and 10 049 ulcerative colitis [UC]) from 2011 to 2014. Standardized incidence ratios [SIRs] of overall and site-specific cancers in IBD patients in comparison with the general population were calculated. Results: The overall cancer risk was higher in CD patients [SIR, 2.2; 95% confidence interval, 1.5-3.0 in men and 3.3; 2.4-4.5 in women] and UC patients [1.9; 1.6-2.3 in men and 1.9; 1.5-2.4 in women]. There were significantly increased risks for the following cancers: small bowel cancer [31.2; 3.8-112.8], colorectal cancer [CRC] [3.7; 1.6-7.2] and haematological cancer [4.0; 1.1-10.3] in men with CD; small bowel cancer [61.1; 7.4-220.6], CRC [4.7; 1.5-10.9], liver cancer [15.3; 5.6-33.2], pancreatic cancer [8.6; 1.0-31.0] and haematological cancer [11.0; 3.6-25.7] in women with CD; CRC [2.1; 1.3-3.3] and cancer of the prostate [3.5; 2.1-5.5], brain/central nervous system [6.1; 1.3-17.9] and thyroid [2.2; 1.1-3.9] in men with UC; and CRC [3.0; 1.5-5.3], cancer of the liver [4.4; 1.6-9.7] and cervix uteri [5.7; 2.4-11.1], and haematological cancer [3.5; 1.1-8.1] in women with UC. Women with CD had an increased risk of non-Hodgkin lymphoma [NHL] and leukaemia. Women with UC had an increased risk of NHL. Conclusions: Korean patients with IBD are at increased risk for overall, intestinal and haematological cancer.