The impact of metformin use on survival in kidney cancer patients with diabetes: a meta-analysis

PURPOSE: The effects of metformin on the prognosis of kidney cancer patients with diabetes are in controversial. The present study is conducted to classify the association of metformin use with the survival of patients with kidney cancer. METHODS: Electronic databases, namely PubMed and Web of Science, were used to search the eligible studies up to December, 2016. Pooled hazard ratio (HR) and its corresponding 95% confidence interval (95% CI) were calculated. It was considered as statistically significant when P value was <0.05. RESULTS: Eight cohorts were eligible for the present meta-analysis, including 254,329 kidney cancer patients. The combined HR suggested that the use of metformin could improve the overall survival (OS) (HR 0.643, 95% CI 0.520–0.795, P < 0.001) and cancer-specific survival (CSS) (HR 0.618, 95% CI 0.446–0.858, P = 0.004) in kidney cancer patients. In subgroup analysis, positive associations were found between metformin use and OS/CSS of localized renal cell carcinoma patients (OS: HR 0.634, 95% CI 0.440–0.913, P = 0.014; CSS: HR 0.476, 95% CI 0.295–0.768, P = 0.002). Moreover, we also found that the use of metformin could reduce the risk of death in kidney cancer patients (HR 0.711, 95% CI 0.562–0.899, P = 0.004). CONCLUSION: Our findings suggest that the use of metformin is in favor of the prognosis of patients with kidney cancers. Further investigations are needed to evaluate the prognostic value of metformin on kidney cancer patients.