The purpose of this study is to determine the safety and efficacy of a short course of radiotherapy (40Gy/5 fractions/29 days) for the treatment of high risk prostate cancer currently being managed with primary androgen deprivation therapy (PADT).

Primary Endpoints:

• Acute gastrointestinal (GI) and genitourinary (GU) Common Terminology Criteria for Adverse Events (CTCAE) v3.0 toxicities

Secondary Endpoints:

• Late GI and GU Radiation Therapy Oncology Group (RTOG) toxicities
• Biochemical disease-free survival
• Biopsy positive rate at 3 years
• Quality of life using the Expanded Prostate Cancer Index Composite (EPIC) questionnaire
• Develop a biobank of DNA and serum extracted from blood and urine to analyze and develop new biomarkers for prostate cancer progression or susceptibility to severe toxicity

Inclusion Criteria:

• informed consent obtained
• men > 18 years
• histologically confirmed prostate adenocarcinoma (centrally reviewed)
• high risk prostate cancer, defined as at least one of: clinical stage T3, or gleason score 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
• pelvic girth > 40cm (to ensure visibility of gold seeds on electronic portal imaging)
• large prostate (> 90cm3) on imaging
• severe lower urinary tract symptoms (International Prostate Symptom Score >19 or nocturia > 3)
• No evidence of castrate resistance (defined as PSA < 3ng/mL while testosterone is < 0.7nmol/L). Patients could have been on combined androgen blockade but are excluded if this was started due to PSA progression