EGFR and small cell lung carcinoma: The authors conducted additional subgroup analyses based on type of therapy (chemotherapy vs EGFR-TKI), histology (NSCLC vs small cell lung cancer), and stage (III–IV vs I–IV), which produced consistent results, indicating that the addition of metformin could induce clear improvement in the efficacy of antineoplastic agents in lung cancer patients (Luo et al., 2021).