Impact of metformin on survival outcome in ovarian cancer: a nationwide population-based cohort study

OBJECTIVEInvestigation of new drugs (INDs) is a tremendously inefficient process in terms of time and cost. Drug repositioning is another method used to investigate potential new agents in well-known drugs. This study assessed the survival impact of metformin medication on ovarian cancer. METHODSA national sample cohort of the Korean National Health Insurance Service Data was analyzed. Cox proportional hazards regression was used to analyzing hazard ratios (HRs) and 95% confidence intervals (CIs) after adjusting for underlying diseases and medications as confounding factors for overall survival (OS) and cancer-specific survival (CSS). RESULTSA total of 866 eligible patients were included from among 1,025,340 cohort participants. Among them, 101 (11.7%) were metformin users. No difference in OS was observed between non-users and users. No difference in OS was observed according to age and Charlson Comorbidity Index. Long-term metformin use (≥720 days) was associated with better OS (adjusted HR=0.244; 95% CI=0.090-0.664; p=0.006). A multivariate Cox proportional hazards model showed that long-term metformin use was an independent favorable prognostic factor for OS (HR=0.193; 95% CI=0.070-0.528; p=0.001) but not for CSS (HR=0.599; 95% CI=0.178-2.017; p=0.408). CONCLUSIONLong-term metformin use reduced all-cause mortality, but not CSS in ovarian cancer. Whether metformin itself reduces deaths because of ovarian cancer requires further investigation.