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).