Study of Hypo-fractionated Proton Radiation for Low Risk Prostate Cancer

Inclusion Criteria: * Histologically confirmed prostate adenocarcinoma within 365 days prior to randomization. * History/physical examination with digital rectal examination of the prostate and baseline toxicity assessment within 90 days prior to randomization. * Histological evaluation of prostate biopsy with assignment of a Gleason score to the biopsy material;Gleason score must be in the range of 2-6. \> 6 cores are strongly recommended. * PSA values \< 10 ng/ml within 90 days prior to randomization. Either done prior to biopsy or at least 21 days after prostate biopsy. * Clinical stages T1a-T2a N0 M0 (AJCC Criteria 7th Ed.). Staging must be done by treating investigator. * No pelvic lymph nodes \> 1.5 cm in greatest dimension unless the enlarged lymph node is biopsied and negative. * Patients must be at least 18 years old. * ECOG performance status 0-1 (appendix I) documented within 90 days prior to randomization. * IPSS score \<= 16. * Patients must give IRB approved, study specific, informed consent. * Patients must complete all mandatory tests listed in section 4.0 within the specified time frames. * Patients must be able to start treatment within 56 days of randomization. Exclusion Criteria: * Previous prostate cancer surgery to include: prostatectomy, hyperthermia and cryosurgery. * Previous pelvic radiation for prostate cancer. * Androgen deprivation therapy prior to radiation is allowed. However, it is not acceptable if continued during radiation or as adjuvant therapy. * Active rectal diverticulitis, Crohn's disease affecting the rectum, or ulcerative colitis. * Prior systemic chemotherapy for prostate cancer. * History of proximal urethral stricture requiring dilatation. * Current and continuing anticoagulation with warfarin sodium (Coumadin, heparin, low-molecular weight heparin, Clopidogrel bisulfate (Plavix),or equivalent. (Unless it can be stopped to manage treatment related toxicity, to have a biopsy if needed, or for marker placement). * Any major medical, addictive or psychiatric illnesses which would affect the consent process, completion of treatment and/or interfere with follow-up. Consent by legal authorized representative is not permitted in this study. * Evidence of any other cancer within the past 5 years and \< 50% probability of a 5 year survival. (Prior or concurrent diagnosis of basal cell or non-invasive squamous cell cancer of the skin is allowed).