Current treatment options for high risk localized prostate cancer include radical prostatectomy +/- postoperative radiotherapy, radical radiotherapy with androgen deprivation therapy. Evidence has emerged that prostate cancer has a low α/β ratio in the range of 1-3 Gy. Even with high risk tumors, prostate cancer is hypothesized to have a greater sensitivity to large fraction sizes and high dose per fraction radiotherapy theoretically allows for biological dose escalation with fewer visits and no additional toxicity. Therefore, we hope to determine the toxicity, quality of life, biochemical and pathological control of SBRT for high risk prostate cancer incorporating ENI.

Inclusion Criteria:

• informed consent obtained
• men > 18 years of age
• histologically confirmed prostate adenocarcinoma (centrally reviewed)
• high risk prostate cancer, defined as at least one of clinical stage T3 or Gleason 8-10, or PSA > 20ng/mL

Exclusion Criteria:

• prior pelvic radiotherapy
• anticoagulation medication (if unsafe to discontinue for gold seed insertion)
• diagnosis of bleeding diathesis
• large prostate (>90cm3) on imaging at time of gold seed insertion
• no evidence of castrate resistance (defined as PSA < 3ng/mL while testosterone is < 0.7nmol/L
• definitive regional or distant metastatic disease on staging investigations