Survival Benefit of Metformin Adjuvant Treatment For Pancreatic Cancer Patients: a Systematic Review and Meta-Analysis

Background/Aims: Previous studies on the effect of metformin therapy on survival of pancreatic cancer patients obtained inconsistent findings. To reevaluate the prognostic value of metformin adjuvant treatment, a meta-analysis was carried out. Methods: Relevant articles addressing the association between metformin use and pancreatic cancer survival were electronically searched to identify eligible studies. Pooled hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated to assess the strength of the association. Results: Totally, seventeen studies involving 36791 participants were included. Overall, metformin use was found to be significantly associated with a favorable OS (HR=0.88, 95% CI=0.80-0.97). Subgroup analyses by ethnicity showed a significantly reduced risk of death for metformin users compared with non-users in Asians (HR=0.74, 95% CI=0.58-0.94) but nonsignificant in Caucasians. When stratified by clinical stage, a remarkable reduction of mortality risk in patients at stage I-II treated with metformin (HR=0.76, 95% CI=0.68-0.86) was found as well as the group at stage I-IV (HR=0.88, 95% CI=0.79-0.99), but not in patients at stage III-IV. In the stratification analyses based on treatment strategy, metformin therapy was found to be associated with a better clinical outcome in patients receiving surgery or comprehensive therapy (HR=0.73, 95% CI=0.62-0.87; HR=0.88, 95% CI=0.79-0.97) but not chemotherapy. However, the overall analysis failed to show a significant association between metformin use and DFS (HR=1.54, 95% CI=0.94 -2.50) with only 2 studies enrolled. Conclusion: The current study has evidenced a significant association of metformin adjuvant treatment with the survival benefit for pancreatic cancer patients, suggesting a potentially available option for the treatment. Further investigation is needed.