Use of metformin and survival of patients with high-grade glioma.

High-grade glioma (HGG) is associated with poor prognosis. Drug repurposing evolves as new modality to improve standard therapy. The antidiabetic drug metformin has been found to inhibit glioma cell growth in vitro and in vivo. The aim of the present retrospective cohort study was to evaluate the survival of patients with HGG with or without treatment with metformin, based on a large cohort of a cancer registry. The analysis included 1,093 patients with HGG diagnosed between 1998 and 2013 from the population-based clinical cancer registry Regensburg (Germany), which covers 2.1 Mio inhabitants and 98% of all cancer diagnoses. We performed multivariable adjusted Cox-regression analyses. Hazard Ratios (HRs) with 95% Confidence Intervals (CIs) for overall survival (OS) and progression-free survival (PFS) of patients with HGG with or without treatment with metformin were obtained. Use of metformin was associated with a significantly better overall and progression-free survival of patients with WHO grade III glioma (HR for OS = 0.30; 95% CI = 0.11-0.81, HR for PFS = 0.29; 95% CI = 0.11-0.78), while there were no significant relations with OS (HR = 0.83; 95% CI = 0.57-1.20) or PFS (HR = 0.85; 95% CI = 0.59-1.22) in patients with WHO grade IV glioma. In conclusion, use of metformin is associated with better overall and progression-free survival of patients with WHO grade III. Possible underlying mechanisms include the higher prevalence of IDH mutations in WHO grade III glioma, which might sensitize to the metabolic drug metformin.