RESUMO
BACKGROUND AND OBJECTIVE: In recent years, many studies have investigated metformin and its effects on lung cancer. However, since previous studies have shown that the relationship between metformin and lung cancer is complicated, we performed a meta-analysis to analyze this relationship. MATERIAL AND METHODS: An electronic database search was conducted using PubMed, Embase, and Cochrane library. Outcomes were quantified with hazard ratios and 95% confidence intervals to compare lung cancer survival in patients treated with or without metformin. RESULTS: Ten studies, involving 4397 participants, were included. In the pooled analysis, we found that metformin treatment significantly improved the survival of lung cancer patients (hazard ratio=0.75, 95% confidence interval: 0.70-0.80; P<0.001). Subgroup analysis showed that when stratified by geographic region, the hazard ratios for overall survival were 0.76 (95% confidence interval: 0.71-0.81, P<0.001) and 0.51 (95% confidence interval: 0.25-0.78, P<0.001) for Western and Asian countries, respectively. When stratified by lung cancer subtype, the hazard ratios for overall survival were 0.78 (95% confidence interval: 0.71-0.84, P<0.001), 0.73 (95% confidence interval: 0.66-0.81, P<0.001), and 0.51 (95% confidence interval: 0.25-0.78, P<0.001) for non-divided, non-small cell, and small-cell lung cancer subtypes, respectively. When stratified by study design, the hazard ratios for overall survival were 0.77 (95% confidence interval: 0.71-0.83, P<0.001) and 0.71 (95% confidence interval: 0.63-0.80, P<0.001) for cohort-based and case-controlled studies, respectively.