Inflammatory Bowel Disease and Risk of Cholangiocarcinoma: Evidence from a Meta-analysis of Population-based Studies

Objective: Patients with inflammatory bowel disease (IBD) have an increased risk of extra-intestinal cancer, whereas its impact on cholangiocarcinoma (CC) remains unknown. The aim of this study was to obtain a reliable estimate of the risk of CC in IBD patients through a meta-analysis of clinical observational studies. Methods: Relevant studies were retrieved by searching PUBMED, EMBASE and Web of Science Databases up to Dec 2013. Four population-based case-control and two cohort studies with IBD were identified. Summary relative risk (RR) and its corresponding 95% confidence interval (CI) were calculated using a random-effects model. Potential sources of heterogeneity were detected using subgroup analyses. Results: The pooled risk estimate indicated IBD patients were at increased risk of CC (RR = 2.63, 95% CI = 1.47-4.72). Moreover, the increased risk of CC was also associated with Crohn's disease (RR = 2.69, 95% CI = 1.59-4.55) and ulcerative colitis (RR = 3.40, 95% CI = 2.50-4.62). In addition, site-specific analyses revealed that IBD patients had an increased risk of intrahepatic CC (ICC) (RR = 2.61, 95% CI = 1.72-3.95) and extrahepatic CC (ECC) (RR = 1.47, 95% CI = 1.10-1.97). Conclusions: This study suggests the risk of CC is significantly increased among IBD patients, especially in ICC cases. Further studies are warranted to enable definite conclusions to be drawn.