An Open-Labeled Pilot Study of Biomarker Response Following Short-Term Exposure to Metformin

Study Groups: If you are found to be eligible to take part in this study, you will be randomly assigned (as in the flip of a coin) to 1 of 2 groups. * If you are in Group 1, you will receive metformin ER. You will have a 2 in 3 chance of being assigned to Group 1. * If you are in Group 2, you will receive no treatment. You will have a 1 in 3 chance of being assigned to Group 2. Study Drug Administration: If you are in Group 1, You will start taking the drug the day after your colonoscopy (or later if your surgery is scheduled to be more than 30 days after the colonoscopy) and will continue to take it until your scheduled surgery (for up to 30 days). During the first week you will take one tablet of metformin-ER by mouth one time each day with food. From the beginning of the second week until your scheduled surgery, you will take two tablets of metformin-ER by mouth one time each day with food. If you have side effects, your dose may be lowered. If you are in Group 2, you will not receive any study drug from the time of your colonoscopy until surgery. Study Visits: On the day of your colonoscopy: * Your medical history will be recorded and you will be asked about any drugs you may be taking. * You will have a physical exam. * Extra tissue samples will be collected during the colonoscopy for routine and biomarker testing. Biomarkers are small pieces of material or substances found in you tissue that may provide information about your condition or the disease. * The study staff will call you 1 week after your colonoscopy and ask about your general health and about any side effects you may be having. On the day before surgery or the day of the surgery itself: * Your weight will be measured. * Blood (about 3 tablespoons) will be drawn for routine tests and for research about the safety of metformin-ER and how it may affect the disease. This routine blood draw will include a pregnancy test if you are able to become pregnant. * You will be asked about your general health and about any side effects you may be having. * During the surgery, extra tissue samples will be collected for biomarker testing. Length of Study: You will be on study for up to 30 days. You will no longer be able to take the study drug if the disease gets worse, if intolerable side effects occur, or if you are unable to follow study directions. Your participation on the study will be over once you have had the surgery. This is an investigational study. Metformin-ER is FDA approved and commercially available for the treatment of type 2 diabetes. Its use in this study is investigational. Up to 23 patients will take part in this study. All will be enrolled at MD Anderson.