Efficacy and Safety of Adjuvant Metformin for Operable Breast Cancer Patients

Inclusion criteria

• Operable Breast cancer patients with BMI ≥ 23 or 100 ≤ FBS < 126
• From 6 month to 2 years since breast cancer operation and at least 4 weeks since chemotherapy or radiotherapy
• No drug use except Tamoxifen
• Normal OTPT & Serum creatinine (<=ULN)
• ECOG performance status 0-2 or Karnofsky PS 60-100%
• Life expectancy > 12
• Absolute neutrophil count ≥ 1.5 x 10^9/L
• Platelets ≥ 100 x 10^9/L
• Pregnancy(-) & without plan for pregnancy
• Sign a written informed consent form

Exclusion criteria

• Type I or II DM or concurrent use of DM control agents
• Prior use of Metformin
• Hypoglycemia (FBS< 70 with clinical symptom)
• Concurrent investigational or commercial agents
• Other diet or drug intervention for weight loss
• Concurrent use of steroid
• Abnormal liver and/or renal function
• Symptomatic congestive heart failure / Cardiac arrhythmia / Angina pectoris
• Ongoing or active infection
• lactic acidosis
• Pregnancy or ongoing breast feeding
• Anorexia, bulimia, nausea due to other disease for longer than 1 month
• Allergies or allergic reactions attributed to oral medications
• Inability to swallow or digest oral medications
• Physical or psychiatric illness that would limit compliance with study protocol
• Participants in other clinical trial