The Anticancer Effect of Metformin Combined with Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Non-small Cell Lung Cancer Patients with or Without Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis

Introduction: Despite the growing evidence for the anticancer effect of metformin or its combination with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), the efficacies and side effects of such strategies in non-small cell lung cancer (NSCLC) patients with or without type 2 diabetes mellitus (T2DM) are not well understood. This meta-analysis was performed to determine the efficacy and side effects of metformin combined with EGFR-TKIs (MET-EGFR-TKIs) for the treatment of NSCLC with or without T2DM. Methods: PubMed and Cochrane Library databases were used to retrieve relevant studies through August 2020 using the keywords "metformin", "EGFR-TKIs" ("gefitinib" or "erlotinib" or "afatinib" or "icotinib" or "dacomitinib") and "lung cancer". The patients in the experimental group received MET-EGFR-TKIs, while those in the control group received only EGFR-TKIs. The outcome analysis reported overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and disease control rate (DCR). Random-effect models and fixed-effect models were used to estimate the combined hazard ratio (HR) and odds ratio (OR) depending on the data heterogeneity. Three studies (including 1996 patients) were included in the current meta-analysis. Results: There were significant differences in PFS (HR 0.84; 95% confidence interval (CI) 0.75-0.95; P = 0.004) and OS (HR 0.77; 95% CI, 0.50-1.04; P < 0.001) between the MET-EGFR-TKI and EGFR-TKI groups. Although the ORR (OR 1.38; 95% CI 0.66-2.88; P = 0.105) and DCR (OR 2.61, 95% CI 0.68-9.95, P = 0.160) were improved, there was no statistical significance. OS subgroup analysis showed that the combination was more effective in NSCLC with T2DM than in NSCLC without T2DM (HR 0.84; 95% CI 0.74-0.95; P < 0.005). Conclusions: MET-EGFR-TKIs provided benefits for PFS and OS, and OS subgroup analysis showed that patients with NSCLC with T2DM received greater benefit than NSCLC patients without T2DM. However, further large-scale, well-designed randomized controlled trials (RCTs) are warranted to confirm the findings in the present investigation.