Metformin is associated with reduced risk of pancreatic cancer in patients with type 2 diabetes mellitus: A systematic review and meta-analysis

Aims: Recent epidemiological studies indicated that use of metformin might decrease the risk of various cancers among patients with type 2 diabetes mellitus (T2DM). However, its influence on pancreatic cancer was controversial. Therefore, we did a meta-analysis of currently available observational studies on the issue. Methods: We did a PubMed and ISI Web of Science search for observational articles. The pooled relative risk (RR) was estimated using a random-effect model. Heterogeneity was evaluated using I-2 statistic. Subgroup analysis was performed to explore the source of heterogeneity and confirm the overall estimates. Publication bias was also examined. Results: The analysis included 11 articles (13 studies) comprising 10 cohort studies and 3 case-control studies. Use of metformin was associated with a significant lower risk of pancreatic cancer [RR 0.63, 95% confidence internal (CI) 0.46-0.86, p = 0.003]. In a total 11 subgroup analyses, 5 provided the consistent result with pooled effect estimates of overall analysis. No publication bias was detected by Begg's (Z = -0.79, p = 0.428) and Egger's test (t = -0.92, p = 0.378). Conclusions: From present observational studies, use of metformin appears to be associated with a reduced risk of pancreatic cancer in patients with T2DM. Further investigation is needed. (C) 2014 Elsevier Ireland Ltd. All rights reserved.