Lack of adequate sample size.

To improve radiation therapy of prostate cancer, the investigators must be able to accurately identify the tumour. By using advanced functional imaging techniques available on state-of-the-art MRI scanners to clearly show the specific location of the tumour inside the prostate, the investigators can use advanced radiation therapy techniques to specifically target the tumor and control it with as few radiotherapy clinic visits as possible. This is different than current techniques which treat the whole prostate gland to the same dose, delivered over 7-8 weeks of daily radiotherapy visits. By increasing the radiation dose to the active tumor while still maintaining adequate radiation dose to the rest of the prostate, the investigators hope to better control prostate cancer and reduce complications to nearby normal tissues.

This project combines advances in functional imaging of prostate cancer and hypofractionation through stereotactic body radiotherapy (SBRT), with an aim to improve tumour control and reduce or maintain normal tissue complications. The strategy will make use of the combined effectiveness of several functional imaging approaches to identify the dominant lesion(s) within the prostate. An SBRT treatment plan will be designed which utilizes 5 fractions to treat the entire prostate gland with an additional boost to the dominant lesion. The lower dose to the entire prostate should reduce normal tissue complications but still be effective in treating prostate cancer while the increased dose to the dominant lesion should improve tumour control. The use of only 5 fractions will reduce the number of patient visits, thus reducing overall treatment costs.

Inclusion Criteria:

• Informed consent
• Age >18 years
• Histologically confirmed and centrally reviewed prostate adenocarcinoma based
• PSA within 60 days
• High risk prostate cancer defined as any one of: clinical stage >= T3, Gleason score >= 8, or PSA >=20 and <50 ng/mL.

Exclusion Criteria:

• Evidence of lymph node metastasis
• Evidence of distant metastases
• Prior pelvic radiotherapy or brachytherapy
• Previous radical prostatectomy, cryotherapy, or high-frequency ultrasound
• Unable to undergo gold seed insertion
• Immunosuppressive medications
• Inflammatory bowel disease
• Unable to undergo MRI
• Previous bilateral orchiectomy
• Previous hormonal therapy including LHRH agonists (leuprolide, goserelin), LHRH antagonists (degarelix), anti-androgens (bicalutamide, flutamide, nilutamide), surgical castration, and estrogens
• Previous finasteride within 14 days.
• Previous dutasteride within 180 days.