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