Androgen-Deprivation Therapy and Radiation Therapy in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS: * Pathologically (histologically or cytologically) proven diagnosis of prostatic adenocarcinoma within 180 days of registration at moderate- to high-risk for recurrence as determined by one of the following combinations: * Gleason score 7-10 + T1c-T2b (palpation) + prostate-specific antigen (PSA) \< 50 ng/mL (includes intermediate- and high-risk patients) * Gleason score 6 + T2c-T4 (palpation) + PSA \< 50 ng/mL OR * Gleason score 6 + \>= 50% (positive) biopsies + PSA \< 50 ng/ml * Gleason score 6 + T1c-T2b (palpation) + PSA \> 20 ng/mL Patients previously diagnosed with low risk prostate cancer undergoing active surveillance who are re-biopsied and found to have unfavorable intermediate risk disease or favorable high risk disease according to the protocol criteria are eligible for enrollment within 180 days of the repeat biopsy procedure. * History and/or physical examination (to include at a minimum digital rectal examination of the prostate and examination of the skeletal system and abdomen) within 90 days prior to registration * Clinically negative lymph nodes as established by imaging (pelvic and/or abdominal CT or MR), (but not by nodal sampling, or dissection) within 90 days prior to registration * Patients with lymph nodes equivocal or questionable by imaging are eligible if the nodes are ≤ 1.5 cm * Patients status post a negative lymph node dissection are not eligible * No evidence of bone metastases (M0) on bone scan within 120 days prior to registration (Na F PET/CT is an acceptable substitute) * Equivocal bone scan findings are allowed if plain films (or CT or MRI) are negative for metastasis * Baseline serum PSA value performed with an FDA-approved assay (e.g., Abbott, Hybritech) within 120 days prior to registration * Study entry PSA should not be obtained during the following time frames: * Ten-day period following prostate biopsy * Following initiation of hormonal therapy * Within 30 days after discontinuation of finasteride * Within 90 days after discontinuation of dutasteride PATIENT CHARACTERISTICS: * Zubrod performance status 0-1 * Absolute neutrophil count (ANC) ≥ 1,500/mm³ * Platelet count ≥ 100,000/mm³ * Hemoglobin (Hgb) ≥ 8.0 g/dL (transfusion or other intervention to achieve Hgb ≥ 8.0 g/dL is acceptable) * No prior invasive (except non-melanoma skin cancer) malignancy unless disease-free for a minimum of 3 years (1,095 days) and not in the pelvis * E.g., carcinoma in situ of the oral cavity is permissible; however, patients with prior history of bladder cancer are not allowed * No prior hematological (e.g., leukemia, lymphoma, or myeloma) malignancy * No previous radical surgery (prostatectomy) or cryosurgery for prostate cancer * No previous pelvic irradiation, prostate brachytherapy or bilateral orchiectomy * No previous hormonal therapy, such as LHRH agonists (e.g., leuprolide, goserelin, buserelin, triptorelin) or LHRH antagonist (e.g. degarelix), anti-androgens (e.g., flutamide, bicalutamide, cyproterone acetate), estrogens (e.g., DES), or surgical castration (orchiectomy) * Prior pharmacologic androgen ablation for prostate cancer is allowed only if the onset of androgen ablation (both LHRH agonist and oral anti-androgen) is ≤ 45 days prior to the date of registration. * No severe, active co-morbidity, defined as any of the following: * 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 or severe liver dysfunction * Acquired immune deficiency syndrome (AIDS) based upon current Centers for Disease Control (CDC) definition * Protocol-specific requirements may also exclude immuno-compromised patients * HIV testing is not required for entry into this protocol * No patients who are sexually active and not willing/able to use medically acceptable forms of contraception * No prior allergic reaction to the hormones involved in this protocol PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior radical surgery (prostatectomy) or cryosurgery 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., leuprolide, goserelin, buserelin, triptorelin) or LHRH antagonist (e.g., degarelix), anti-androgens (e.g., flutamide, bicalutamide, cyproterone acetate), estrogens (e.g., diethylstilbestrol (DES) ), or surgical castration (orchiectomy) * No prior pharmacologic androgen ablation for prostate cancer unless the onset of androgen ablation is ≤ 45 days prior to the date of registration * No finasteride within 30 days prior to registration * No dutasteride or dutasteride/tamsulosin (Jalyn) within 90 days prior to registration * No prior or concurrent cytotoxic chemotherapy for prostate cancer * Prior chemotherapy for a different cancer is allowable * No prior radiotherapy, including brachytherapy, to the region of the study cancer that would result in overlap of radiation therapy fields