A randomized controlled open-label trial in patients with high risk prostate cancer. Eligible and consenting patients will be randomly allocated to receive stereotactic body radiotherapy (SBRT) boost to prostate or conventional radiotherapy boost to prostate in 1:1 ratio. Prostate radiotherapy boost will be administered after standard pelvic radiotherapy. Subjects will be followed for 24 months post radiation treatment for Quality of Life assessment and toxicity.

In this study we investigate stereotactic body radiotherapy (SBRT) as a boost radiotherapy treatment, following pelvic radiotherapy, in patients with high risk prostate cancer (PrCa) treated with Androgen Deprivation Therapy (ADT). One hundred patients with localized high risk PrCa will receive ADT for a total of 3 years. Three months after initiation of ADT all patients will receive pelvic (lymph node and prostate) treatment of 45Gy in 25 fractions (5 days per week). Then patients will be randomized to receive either The conventional radiotherapy (CRT) of 33 - 35 Gy in 16 fractions (5 days per week - over 22 days) (comparator arm) or SBRT boost treatment of 19.5 - 21 Gy in three fractions (1 treatment per week - over 22days) (experimental arm). SBRT boost treatment will be delivered with either cyberknife or VMAT technique.

Inclusion Criteria:

• Histological and or clinical diagnosis of high risk adenocarcinoma of the prostate within six months of entry (stage T3 or higher and/or Gleason score 8 or higher and/or initial PSA level above 20;)
• No radiographic evidence of metastatic disease to the abdomen, lymph nodes, bone or other distant organs; determined by standard staging investigations (bone scan and CT-scan of the abdomen and pelvis) or incidental findings (localized N0, M0 disease)
• Patient is able to complete the quality of life questionnaires in English.
• Informed consent obtained

Exclusion Criteria:

• • Histological diagnosis of carcinoma of the prostate more than six months prior to potential registration date;
• Previous treatment for carcinoma of the prostate (other than biopsy or TURP), including bilateral orchiectomy;
• Patients previously on more than twelve weeks of hormone therapy for their PrCa;
• Past history of other malignancies except: adequately treated non-melanoma skin cancer or other solid tumours curatively treated with no evidence of disease for more than 3 years;
• Contraindications to placement of gold seeds for daily prostate localization;
• Previous pelvic RT and/or significant pelvic surgery;
• Severe diverticular or inflammatory bowel disease (as determined by the treated radiation oncologist)
• Previous hip replacement
• PSA over 50
• IPSS 20 or higher
• TRUS-based prostate
• volume of > 80 cc