Metformin for Chemoprevention of Lung Cancer in Overweight or Obese Individuals at High Risk for Lung Cancer

This phase II trial determines the effect of metformin extended release on the risk for developing lung cancer in overweight/obese patients that are at high-risk for developing lung cancer. Metformin is widely used to treat type II diabetes and has a long history of safety and minimal side effects. At similar dosage, the drug may have potential anti-cancer activity. Metformin use has been associated with improved survival in patients with non-small cell lung carcinoma, a specific type of lung cancer, and it has also been shown to enhance immune mobilization against tumors. This trial aims to see whether metformin extended release as a preventative treatment may lower the chance of developing lung cancer, and whether it may help patients\' immune system learn (\"reprogram\") to lower a certain type of immune cell (called regulatory T cells) that are linked to tumor development.