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

Inclusion Criteria:

1. Age between 18- 75 years
2. Colonic lesion that should be removed surgically:
3. 2.a. CRC that is potentially resectable and not requiring neoadjuvant treatment.
4. 2.b. Endoscopically non-resectable adenoma.
5. 2.c. Familial Adenomatous Polyposis (FAP) patient that requires colectomy or proctocolectomy.
6. Need for perioperative colonoscopy as a part of standard of care evaluation:
7. 6.a. CRC or adenoma for which the colorectal surgeon requires a preoperative colonoscopy or sigmoidoscopy for any reason, including but not limited to:
8. 6.a.a. No outside colonoscopy
9. 6.a.b. No outside pathology
10. 6.a.c. Partially obstructing tumor or
11. 6.a.d. Otherwise unsatisfactory outside colonoscopy
12. 6.a.e. Rectal cancer requiring EUS
13. 6.a.f. Second opinion on adenoma regarded as endoscopically non-resectable on outside colonoscopy; or
14. 6.b. Patient found on initial MDACC colonoscopy to have CRC or endoscopically non-resectable adenoma, most commonly patients undergoing average or high risk (familial, history of adenoma) screening colonoscopy.
15. Ability to give informed consent.
16. Diabetic patients are eligible but they may be excluded if they are taking Metformin, insulin or sulfonylureas.

Exclusion Criteria:

1. Patients with renal insufficiency defined as serum creatinine \>= 1.4 mg/dl for females and \>= 1.5 mg/dl for males
2. Pregnant or nursing women
3. A malignancy currently under active therapy
4. Unstable angina
5. Uncontrolled ischemic cardiac disease or symptomatic congestive heart failure (e.g. Class III or IV New York Heart Association's Functional Classification)
6. Current usage of Metformin
7. Current usage of insulin, sulfonylureas
8. History of lactic acidosis
9. Chronic liver disease or cirrhosis
10. Inability to give informed consent
11. Other investigational drugs within the past one year or concurrently
12. Known hypersensitivity or intolerance to Metformin