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

Abstract 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.