Radiation Therapy in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed diagnosis of adenocarcinoma of the prostate within 180 days of randomization * History/physical examination with digital rectal examination of the prostate within 60 days prior to registration * Histological evaluation of prostate biopsy with assignment of a Gleason score to the biopsy material; Gleason scores 2-6 within 180 days of randomization * Clinical stage T1-2a (AJCC 7th edition) within 90 days of randomization * Prostate-specific antigen (PSA) \< 10 ng/mL within 60 days prior to registration; * PSA should not be obtained within 10 days after prostate biopsy * No evidence of distant metastases * No regional lymph node involvement PATIENT CHARACTERISTICS: * Zubrod performance status 0-1 * Willingness and ability to complete the Expanded Prostate Cancer Index Composite (EPIC) questionnaire * No prior or concurrent invasive malignancy (except non-melanomatous skin cancer) or lymphomatous/hematogenous malignancy unless continually disease-free for a minimum of 5 years (for example, carcinoma of the oral cavity is permissible; however, patients with prior history of bladder cancer are not allowed) * No severe, active 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 and/or coagulation defects * Laboratory tests for liver function and coagulation parameters are not required for entry into this protocol * Acquired Immune Deficiency Syndrome (AIDS) based upon current Center for Disease Control (CDC) definition * HIV testing is not required for entry into this protocol * Protocol-specific requirements may also exclude immuno-compromised patients PRIOR CONCURRENT THERAPY: * No prior radical surgery (prostatectomy), cryosurgery, or high-intensity focused ultrasonography (HIFU) for prostate cancer * No prior pelvic irradiation, prostate brachytherapy, or bilateral orchiectomy * No prior hormonal therapy, such as luteinizing hormone-releasing hormone (LHRH) agonists (e.g., goserelin, leuprolide) or LHRH antagonists (e.g., degarelix), anti-androgens (e.g., flutamide, bicalutamide), estrogens (e.g., diethylstilbestrol (DES)), or surgical castration (orchiectomy) * No finasteride within 30 days prior to registration * Prostate-specific antigen (PSA) should not be obtained prior to 30 days after stopping finasteride * No dutasteride within 90 days prior to registration * PSA should not be obtained prior to 90 days after stopping dutasteride * No prior or concurrent cytotoxic chemotherapy for prostate cancer * Patients on Coumadin or other blood-thinning agents are eligible for this study * No concurrent 3D-conformal radiation therapy