Prognostic value of metformin in cancers: An updated meta-analysis based on 80 cohort studies

Experiments have shown that metformin can inhibit cancer cell growth, but clinical observations have been inconsistent, so we pooled the currently available data to evaluate the impact of metformin on cancer survival and progression. METHODS: PubMed, web of science, Embase, and Cochrane databases were searched. Pooled hazard ratios (HRs) were identified using a random-effects model to estimate the strength of the association between metformin and survival and progression in cancer patients. RESULTS: We incorporated 80 articles published from all databases which satisfied the inclusion criterion. It showed that metformin was associated with better overall survival (hazard ratio [HR] = 0. 81; 95% confidence interval [CI]: [0.77–0.85]) and cancer-specific survival (HR = 0.79; 95% CI: [0.73–0.86]), and metformin was associated with progression-free survival (HR = 0.76; 95% CI: [0.66–0.87]). In patients with diabetes mellitus, the HR of overall survival was 0.79(95% CI: [0.75–0.83]), progression-free survival was 0.72(95% CI: [0.60–0.85]), and the cancer-specific survival was 0.76(95% CI: [0.68–0.86]). It was proposed that metformin can improve the prognosis of cancer patients with diabetes mellitus. CONCLUSION: Based on cohort studies, metformin therapy has potential survival benefits for patients with malignancy, especially with the greatest benefits seen in breast cancer on overall survival, progression-free survival, and cancer-specific survival. And metformin also showed potential benefits in cancer-specific survival in colorectal and prostate cancer.