Hypofractionated Proton Beam Therapy for Localized Prostate Cancer

Inclusion Criteria: * Histologically confirmed diagnosis of adenocarcinoma of the prostate within one year of study entry; evaluation can happen outside of MD Anderson as long as histological confirmation takes place at MD Anderson * History/physical examination with digital rectal examination of the prostate within 90 days prior to registration * Histological evaluation of prostate biopsy with assignment of a Gleason score to the biopsy material demonstrating Gleason score 2-7 within 365 days of registration * Clinical stage T1-2b (American Joint Committee on Cancer \[AJCC\] 7th edition) and PSA \< 20 ng/mL within 90 days prior to registration; PSA should not be obtained within 10 days after prostate biopsy * Zubrod performance status 0-1 within 90 days prior to registration * Patient must be able to provide study-specific informed consent prior to study entry * Willingness and ability to complete the EPIC questionnaire Exclusion Criteria: * Prior or concurrent invasive malignancy (except non-melanomatous skin cancer or lymphomatous/hematogenous malignancy) unless continually disease free for a minimum of 5 years * Evidence of distant metastases * Regional lymph node involvement * Previous prostatectomy, cryosurgery, or high intensity focused ultrasound (HIFU) for prostate cancer * Previous pelvic radiation or prostate brachytherapy * Active and severe medical co-morbidity defined as follows: unstable angina and/or congestive heart failure requiring hospitalization within the last 6 months, transmural myocardial infarction within the last 6 months, acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration, chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of registration, hepatic insufficiency resulting in clinical jaundice, active inflammatory bowel disease (Crohn's disease or ulcerative colitis), diagnosed connective tissue disorder, or congenital coagulation defects (patients on medical therapy with Coumadin or other blood thinning agents are eligible for participation)