Metformin Use in Relation With Survival Outcomes of Patients With Renal Cell Carcinoma

PurposeTo examine the effect of metformin use on survival outcomes in patients with renal cell carcinoma (RCC).MethodsRetrospective analysis of 1528 RCC patients from 2 centers between 1992 and 2012 was conducted. A total of 390 diabetics with confirmed metformin use were included in the final analysis, with a median follow-up of 43.1 months. Primary outcomes were disease-free survival (DFS) and cancer-specific survival (CSS). Cox regression models were performed to evaluate the effects of potential predictors on DFS and CSS, following stratification of patients into local and metastatic disease.ResultsWe identified 290 diabetics with localized and 100 with metastatic RCC. There were no clinicopathologic differences in the profiles of metformin users and non-metformin users. For patients with localized RCC, metformin users had significantly better DFS (hazard ratio, 0.47; P < .01) and CSS (hazard ratio, 0.21; P < .01) than non-users. There was no difference in CSS between metformin users and non-metformin users in diabetics with metastatic RCC (hazard ratio, 0.78; P = .286). Limitations include retrospective design and lack of data on metformin dosage and duration of use.ConclusionsMetformin use is correlated with improved survival in patients with localized RCC, but not in metastatic RCC. Future studies should focus on its potential mechanisms and clinical utility.