Androgen Suppression With Stereotactic Body or External Beam Radiation Therapy (ASSERT)

Inclusion Criteria:

1. Pathological diagnosis of prostate cancer within 365 days prior to registration.
2. Disease must be Canadian Consensus (GUROC) high and intermediate risk with probability of pelvic nodal involvements \<15% by the Updated Partin Tables.

   * High risk is defined by any of: ≥T3a, PSA \> 20, or Gleason ≥ 8
   * Intermediate risk is defined by: T1/T2 and/or Gleason ≤ 7 and/or PSA ≤20 and not low risk
3. Disease must be T1 or T2 clinically
4. Prostate specific antigen (PSA) and testosterone level (TTT) must be done not more than 60 days before registration. If androgen deprivation therapy is started before registration, PSA and TTT should be done not more than 60 days prior to commencement of androgen deprivation therapy.
5. For high risk patients, negative pelvis CT scan and bone scan for metastases not more than 60 days before registration. If androgen deprivation therapy is started before registration, pelvis CT scan and bone scan should be done not more than 60 days prior to commencement of androgen deprivation therapy. For intermediate risk patients, pelvis CT scan and bone scan are optional.
6. Commencement of androgen deprivation therapy is allowed before registration. However, the lead time must allow for completion of the radiation treatment within 6 months and 18 months of the androgen deprivation therapy treatment duration for intermediate and high risk disease respectively.
7. History/physical examination with digital rectal examination of the prostate within 60 days of registration or commencement of androgen deprivation therapy.
8. Life expectancy of at least 5 years
9. Eastern Cooperative Oncology Group (ECOG) performance status 0 - 2
10. No contraindication for 6 months and 18 months of androgen deprivation therapy respectively for intermediate and high risk disease.

Exclusion Criteria:

1. Clinical evidence of extra-prostatic disease extension
2. Clinical evidence of prostate volume \> 90 cc prior to randomization
3. Prior history of inflammatory bowel disease
4. Prior history of invasive malignancy (except non-melanomatous skin cancer) or lymphomatous/hematogenous malignancy unless continually disease free for a minimum of 5 years. All patients with in situ carcinoma are eligible for this study (for example, carcinoma in situ of the oral cavity is eligible) except patients with carcinoma of the bladder (including in situ bladder cancer or superficial bladder cancer).
5. Previous pelvic radiation
6. Presence of a hip prosthesis
7. Evidence of pelvic nodal involvement or distant metastases