Effect of Metformin on Biomarkers of Colorectal Tumor Cell Growth

Inclusion Criteria:

Male or female, all races and ethnicities are eligible
Age equal to or greater than 18 years of age
All subjects should have a pathological/histological diagnosis of colorectal cancer.
Clinical diagnosis of stage I, II, III or IV colon cancer or stage I, II, III or IV rectal cancer; cancer may be primary including a secondary primary
Candidate for elective surgery(for removal of primary) or endoscopic biopsy
ECOG Performance status of 0 - 2
Adequate renal, liver, and bone marrow function
Hb: (adequate for surgical intervention, with transfusion if necessary)
WBC: (normal range)
Platelets: (180K/cmm)
LFTs: Normal bilirubin (< 2.0mg/dL), AST/ALT (2xULN)
Renal function: normal creatinine
Subjects must have signed informed consent
Female subjects must either not be of child-bearing potential or must have a negative urine pregnancy test within 7 days of beginning the drug or placebo treatment. Subjects are considered not of child-bearing potential if they are surgically sterile or they are postmenopausal for greater than 12 months.

Exclusion Criteria:

Previously diagnosed with diabetes mellitus Type 1 or Type 2.
Currently taking biguanides, sulfonylurea drugs, thiazolidinediones, insulin, or mTOR inhibitors or having taken any of these medications during the 12 weeks prior to study participation.
Currently taking any non-steroidal anti-inflammatory drugs (NSAIDs) or aspirin and unable to stop such medications due to a present medical condition.
Clinical symptoms of gastrointestinal obstruction or bleeding and consideration for immediate surgery or immediate neoadjuvant chemoradiation.
Familial Adenomatous Polyposis (FAP), hereditary non-polyposis colorectal cancer (HNPCC), Putz-Jeghers disease, ulcerative colitis, or Crohn's disease.
Pregnant or lactating.
History of lactic or other metabolic acidosis.
Known hypersensitivity to Metformin.
Uncontrolled infectious disease.
History of Positivity for human immunodeficiency virus (HIV).
History of congestive heart failure requiring pharmacologic treatment.
History of excessive alcohol abuse, defined by a habitual intake of more than three drinks daily.
Previous or concurrent malignancies, except non-melanoma skin cancers, unless curatively treated and with no evidence of recurrence for > 5 years, with the exception of prior CRC which has been treated and the patient has been in remission and the current primary tumor is a second CRC.
Unable to swallow and retain oral medication.
Mal-absorption syndrome, disease affecting gastrointestinal function, or previous resection of the stomach or small bowel.
Current use of medications for weight loss.
Currently taking cimetidine, thiazide diuretics or cephalexin. If a patient needs some of these agents, alternative agents should be substituted.
If the physician feels that the candidate is not suitable for the study, he/she will be excluded.