Diabetes mellitus and the risk of cholangiocarcinoma: an updated meta-analysis

INTRODUCTION A number of studies have shown that diabetes mellitus is implicated in susceptibility to several cancers. However, the relationship between diabetes and cholangiocarcinoma remain unclear. AIM To quantitatively assess the relationship between diabetes and incidence of cholangiocarcinoma in cohort and case-control studies. MATERIAL AND METHODS A literature search was performed for entries from 1996 to 2014 using the PubMed and EMBASE databases. Studies were included if they reported odds ratios (OR) and corresponding 95% CI of cholangiocarcinoma with respect to diabetes mellitus. RESULTS Twenty studies met the inclusion criteria, which included fifteen case-control studies and five cohort studies from Asia (n = 11), the United States (n = 5), and Europe (n = 4). Compared with individuals without diabetes, the pooled OR of cholangiocarcinoma was 1.74 (95% CI: 1.62-1.87, p = 0.568 for heterogeneity) for patients with diabetes, ICC (summary RR, 1.93; 95% CI: 1.65-2.25; p = 0.037 for heterogeneity), and ECC (summary RR, 1.66; 95% CI: 1.39-1.98; p = 0.001 for heterogeneity). The funnel plot revealed no evidence for publication bias concerning diabetes and the risk of CC (including ICC and ECC). CONCLUSIONS The findings from this meta-analysis suggest that diabetes may increase the risk of cholangiocarcinoma. This relationship needs to be confirmed by further follow-up studies.