Chemotherapy and Radiation Therapy With or Without Metformin Hydrochloride in Treating Patients With Stage III Non-small Cell Lung Cancer

PRIMARY OBJECTIVES: I. To determine whether metformin hydrochloride (MET) added to chemoradiotherapy can improve progression-free survival (PFS) in patients with locally advanced non-small cell lung cancer (NSCLC). SECONDARY OBJECTIVES: I. Determine the effects of MET on overall survival (OS), time to local-regional progression (LRP), and time to distant metastasis (DM). II. Evaluate the effect of MET on chemoradiotherapy toxicity (Common Terminology Criteria for Adverse Events, version 4 \[CTCAE, v. 4\]) within 1 year of completion of all treatment. III. Collect biospecimens to develop biomarkers of MET activity. OUTLINE: Patients are randomized to 1 of 2 treatment arms. After completion of study treatment, patients are followed up at 4-6 weeks, every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.