Effects of Metformin on Survival and Toxicity in Patients with Metastatic Non-Small Cell Lung Cancer Treated with Nivolumab

Background and Objectives: This study evaluated the effects of concurrent metformin use on clinical outcomes in patients with metastatic non-small cell lung cancer (NSCLC) treated with nivolumab. Materials and Methods: A total of 152 patients were analyzed, including 110 non-users and 42 metformin users with type 2 diabetes. Results: A significant gender imbalance was observed, with a higher proportion of females in the metformin group (33.3% vs. 8.2%, p < 0.05). The metformin group showed a numerically higher body mass index (BMI), though not statistically significant (26.53 vs. 24.97, p = 0.065). Overall survival was significantly longer in the metformin group (5.02 ± 3.93 vs. 4.6 ± 3.79 years, p < 0.05), while progression-free survival did not differ significantly (1.32 ± 0.97 vs. 1.04 ± 0.75 years, p = 0.385). Although most adverse events were similar across groups, grade 3–4 thrombocytopenia was more frequent in metformin users (p < 0.05). Multivariate analysis showed that increased nivolumab treatment cycles were significantly associated with reduced mortality risk (OR = 0.64, 95% CI: 0.54–0.75, p < 0.05). Conclusions: These findings suggest that concurrent metformin use may enhance overall survival but also increase hematologic toxicity, warranting closer monitoring in NSCLC patients receiving nivolumab.