The purpose of this study is to find out the effects (good and bad) of highly focused radiation on you and your prostate cancer. The purpose of this evaluation is to see if this treatment causes fewer side effects that other standard treatment approaches, and to evaluate the effect of this treatment on your prostate tumor and your quality of life over time.

Inclusion Criteria:

• Histologically proven prostate adenocarcinoma
• Clinical stage T1a-T3, N0-Nx, M0-Mx
• Patients belonging in one of the following risk groups: (1) LOW RISK: CS T1a-T2a, Gleason 2-6, PSA<10, Nx-0, Mx-0; (2) INTERMEDIATE RISK: CS T2b, Gleason ≤7, PSA<20, Nx-0, Mx-0, or CS T1a-T2b, Gleason 2-6, PSA≥10 & <20, Nx-0, Mx-0, or CS T1a-T2b, Gleason 7, PSA≤20, Nx-0, Mx-0; or (3) HIGH RISK: CS T2c-T3, any Gleason, any PSA, or CS T1-3, Gleason ≥8 and/or PSA≥20
• Karnofsky performance status 70-100
• Hormone therapy: includes LHRH agonists (e.g. leuprolide, goserelin, triptorelin), antagonists (e.g. degarelix), peripheral blockers (e.g. flutamide, bicalutamide, nilutamide), estrogens (e.g. DES) and bilateral orchiectomy
• Low and Intermediate risk groups: no hormone ablation for two months prior to enrollment, or during treatment
• High risk group: three hormone therapy regimens are allowed
• 5-alpha reductase inhibitors (e.g., finasteride or dutasteride) are allowed

Exclusion Criteria:

• Prior prostatectomy or cryotherapy of the prostate
• Prior high-dose radiotherapy to the prostate or lower pelvis
• Implanted hardware or other material that would prohibit appropriate treatment planning or treatment delivery, in the investigator's opinion