Prevention of Metabolic Syndrome and Increased Weight Using Metformin Concurrent to Androgen Deprivation Therapy and Radiotherapy for Locally Advanced Adenocarcinoma of the Prostate

This study will examine the role of Metformin as a means to prevent increases in weight as well as the prevalence and severity of metabolic syndrome, with their associated morbidity, amongst men with locally advanced, biopsy confirmed adenocarcinoma of the prostate (PCa) that are planned to receive curative intent therapy with androgen deprivation therapy (ADT) and external beam radiotherapy (EBRT) to the prostate. Males of any age with biopsy confirmed high tier intermediate risk PCa (Gleason score 7 and PSA 10-20) or high risk PCa (any T3; and/or Gleason Score ≥ 8.0; and/or PSA ≥ 20 ng/mL) ECOG 0 to 1, non-diabetic with no evidence of metastatic PCa will be randomized to either: Group A: Metformin 500mg PO TID x 30-36 months total, with neoadjuvant and adjuvant ADT x18-36 months and EBRT of 46 Gy/23# to pelvic lymph nodes (optional); plus prostate boost to 78 Gy/39# or brachytherapy boost (110-115 Gy) or hypofractionated equivalent OR Group B: Identical placebo TID x 20-36 months total, with neoadjuvant and adjuvant ADT x18-36 months and EBRT of 46 Gy/23# to pelvic lymph nodes (optional); plus prostate boost to 78 Gy/39# or brachytherapy boost (110-115 Gy) or hypofractionated equivalent A planned sample size of 104 patients will provide 97% power for a 2-tailed α of 0.05 to detect 4 kg difference in weight at 12 months of follow-up.