Metformin use and lung cancer survival: a population-based study in Norway

BACKGROUND: We assessed associations between metformin use and survival in a nationwide Norwegian cohort of lung cancer (LC) patients. METHODS: The study linked 22,324 LC patients from the Cancer Registry of Norway diagnosed 2005–2014 with the Norwegian Prescription Database. We estimated associations of pre- and post-diagnostic metformin use with overall survival (OS) and LC-specific survival (LCSS) using multivariable time-fixed and time-dependent Cox regression. RESULTS: Pre-diagnostic metformin use was not associated with improved survival in all patients. Nevertheless, pre-diagnostic metformin use was associated with better LCSS in squamous cell carcinoma (SCC) patients (hazard ratio (HR) = 0.79; 95% confidence interval (CI) 0.62–0.99) and in patients with regional stage SCC (HR = 0.67; 95%CI 0.47–0.95). Post-diagnostic metformin use was associated with improved LCSS in all patients (HR = 0.83; 95%CI 0.73–0.95), in patients with SCC (HR = 0.75; 95%CI 0.57–0.98), regional stage LC (HR = 0.74; 95%CI 0.59–0.94), and regional stage SCC (HR = 0.57; 95%CI 0.38–0.86). OS showed similar results. Analyses of cumulative use showed a dose-response relationship in all patients, patients with adenocarcinoma and SCC, and with regional and metastatic LC. CONCLUSIONS: Metformin use was associated with improved survival, especially LCSS in patients with regional stage SCC. Further prospective studies are required to clarify the role of metformin in LC treatment.