Advanced Lung Cancer Treatment With Metformin and Chemo-Radiotherapy

Inclusion Criteria: 1. Age \>/=18 to \</= 80 years of age. 2. Unresected and pathologically (histologic) proven Stage 3a or Stage 3b NSCLC of adenocarcinoma, squamous cell, large cell or mixed histology, diagnosed within three months of study randomization. 3. Non-metastatic disease staged by: CT-chest and upper abdomen, brain MRI or contrast-enhanced CT within 12 weeks and physical examination and whole body FDG-PET/CT scan within 8 weeks prior to study randomization. Exclusion Criteria: 1. Eastern Cooperative Oncology Group (ECOG) performance status \>2. 2. More than 10% weight loss in the past 3 months. 3. Diabetic patient or anyone currently taking Metformin, insulin or other anti-hyperglycemic therapy. 4. Pulmonary Function Test (PFTs) (within the last 12 weeks) with Forced Expiratory Volume (FEV)1 \< 1.2 litres per second or less than 50% of predicted. 5. Complete Blood Count (CBC) and biochemical renal and liver function profiles that do not permit chemotherapy treatment (as per institutional standard of care). 6. Fasting blood sugar levels of \>/= 7.0 mmol per litre (within the last 12 weeks). 7. Prior systemic chemotherapy for lung cancer. 8. Prior radiotherapy that would overlap with the planned treatment area. 9. Prior invasive malignancy within the past 3 years (except non-melanomatous skin cancer non-invasive carcinoma in-situ of the breast, oral cavity or cervix). 10. Known Acquired Immune Deficiency Syndrome (AIDS). 11. Patients with increased risk for lactic acidosis: * severe congestive heart failure (NYHA: class III or IV), * history of metabolic acidosis, * alcoholic intake of \> 3 drinks daily, * severe liver disease, * renal failure 12. Known hypersensitivity or allergy to Metformin. 13. Known pregnancy or lactating female patient. 14. Geographic inaccessibility for follow-up. 15. Inability to provide informed consent.