Metformin Association with Lower Prostate Cancer Recurrence in Type 2 Diabetes: a Systematic Review and Meta-analysis

Background: Accumulating evidence suggests that metformin possesses anticarcinogenic properties, and itsuse is associated with favorable outcomes in several cancers. However, it remains unclear whether metformininfluences prognosis in prostate cancer (PCa) with concurrent type 2 diabetes (T2D). Materials and
Methods:We searched PubMed, EMBASE, and the Cochrane Library from database inception to April 16, 2014 withoutlanguage restrictions to identify studies investigating the effect of metformin treatment on outcomes of PCa withconcurrent T2D. We conducted a meta-analysis to quantify the risk of recurrence, progression, cancer-specificmortality, and all-cause mortality. Summary relative risks (RRs) with corresponding 95% confidence intervals(CIs) were calculated. Publication bias was assessed by Begg’s rank correlation test.
Results: A total of eightstudies fulfilled the eligibility criteria. We found that diabetic PCa patients who did not use metformin were atincreased risk of cancer recurrence (RR, 1.20; 95%CI, 1.00-1.44), compared with those who used metformin.A similar trend was observed for other outcomes, but their relationships did not reach statistical significance.Funnel plot asymmetry was not observed among studies reporting recurrence (p=0.086).
Conclusions: Ourresults suggest that metformin may improve outcomes in PCa patients with concurrent T2D. Well-designedlarge studies and collaborative basic research are warranted.