Metformin in Preventing Androgen Deprivation Therapy Induced Insulin Resistance and Metabolic Syndrome

Inclusion criteria

• ≥ 18 years of age
• ECOG ≤ 1
• Histologically confirmed prostate cancer of early or locally advanced stage, or metastatic prostate cancer with bone involvement only (≤ 5 sites of bone metastases only)
• Plan to receive ≥ 6 months continuous androgen deprivation therapy by a GnRH agonist
• Patients who are to receive antiandrogens with GnRH agonists are not excluded from the study. But the form, dose and duration of antiandrogen treatment should be recorded.
• Adequate renal function (Creatinine ≤ 177mMol/L and GFR >30 mls/min )
• Adequate hepatic function (Bilirubin must be ≤ 1.5 x upper limit of normal range, ALT and ALP must be ≤ 2.5 x upper limit of normal)

Exclusion criteria

• Visceral involvement
• > 5 sites of bone metastases
• History of confirmed diabetes mellitus (patients with impaired fasting glucose or impaired glucose intolerance will not be excluded) 12
• Treatment with medications that may alter glucose or insulin level within 3 months (including insulin, oral hypoglycemic agents, systemic corticosteroid of any dosage, atypical antipsychotic drugs of any dose)
• Malignant disease other than prostate cancer at the time of enrolment
• Bilateral orchiectomy
• Previous androgen deprivation therapy by a GnRH agonist or anti-androgen within last 12 months(patient who had a GnRH agonist more than 12 months ago are allowed if their testosterone levels are in the normal range at the time of recruitment)
• Chemotherapy within 6 months
• History of lactic acidosis
• Cardiac or respiratory insufficiency, severe infection that is likely to increase the risk of lactic acidosis
• Medical or psychiatric conditions that compromise the patient's ability to give informed consent