Risk of cancer in patients with irritable bowel syndrome: A nationwide population-based study

Purpose: The aim of our study was to evaluate the overall cancer risk among patients with the irritable bowel syndrome (IBS) by using a nationwide population-based data set. Methods: We obtained data on newly diagnosed IBS patients (age ≥ 20 years) without antecedent cancer from the Taiwan National Health Insurance Research Database for the period between 2000 and 2010. Standardized incidence ratios (SIRs) were calculated for various types of cancer in the IBS patients. Results: A total of 1,043 people among the 29,838 IBS patients had developed cancer, and the follow-up was 139,185 person-years (median, 4.56 years), leading to a significantly increased SIR (1.18; 95% confidence interval [CI]) = 1.11-1.26) among all cancer types. However, after excluding cancer that developed within the first year after IBS diagnosis, the increased SIR of overall cancer was nonsignificant. In particular, the IBS patients exhibited an increased risk of cancers of the colon and rectum (SIR = 1.51; 95% CI = 1.31-1.73), liver and biliary tract (SIR = 1.40; 95% CI = 1.21-1.62), pancreas (SIR = 1.56; 95% CI = 1.02-2.28), and kidney (SIR = 1.56; 95% CI = 1.10-2.15). Conclusions: An increased SIR in IBS patients was observed only within the first year of IBS diagnosis. The findings of this study might have resulted from detection bias, localized symptoms, or paraneoplastic syndromes associated with IBS-like symptoms. Additional prospective studies are necessary to confirm these findings.