Inclusion Criteria:

          -  Patients post-prostatectomy with baseline Gleason >= 7 (per prostatectomy pathology)
             and baseline PSA prior to the start of androgen deprivation therapy nadir >= 0.2 ng/ml
             (post-operative value is never undetectable) obtained prior to step 1 registration

          -  Baseline testosterone level obtained post prostatectomy prior to the start of androgen
             deprivation therapy and prior to step 1 registration

          -  Pathologically (histologically) proven diagnosis of adenocarcinoma of the prostate as
             confirmed at time of prostatectomy; prostatectomy must have been performed =< 365 days
             (1 year) prior to step 1 registration

          -  Primary treatment with radical prostatectomy

          -  Any type of radical prostatectomy is permitted, including retropubic, perineal,
             laparoscopic or robotically assisted

          -  Prior ablative treatment for treatment of benign prostatic hypertrophy or focal
             high-intensity focused ultrasound therapy (HIFU) prior to prostatectomy is allowed

          -  Prior androgen deprivation (luteinizing hormone-releasing hormone [LHRH] agonist
             and/or non-steroidal anti-androgen) is allowed if discontinued at least 90 days prior
             to study enrollment and given for =< 90 days duration prior to radical prostatectomy;
             finasteride or dutasteride must be stopped before treatment but should not determine
             eligibility; for patients on prior LHRH analogs, the discontinuation date should be
             calculated based the expected duration of the sustained release injection, not simply
             the injection date of the drug

          -  Pathologically proven to be lymph node negative by pelvic lymphadenectomy (pN0) or
             lymph node status pathologically unknown (undissected pelvic lymph nodes [pNx])

          -  Any pT-stage based on American Joint Committee on Cancer 7th edition is acceptable for
             study entry based on the following diagnostic workup:

               -  History/physical examination within 60 days prior to step 1 registration

               -  No distant metastases, based upon the following minimum diagnostic workup:

               -  A computed tomography (CT) scan of the abdomen and/or pelvis (with contrast if
                  renal function is acceptable; a CT without contrast is permitted if the patient
                  is not a candidate for contrast) or magnetic resonance imaging (MRI) of the
                  pelvis within 120 days prior to step 1 registration; lymph nodes will be
                  non-metastatic unless they measure more than 1.5 cm short axis;

               -  Bone scan within 120 days prior to step 1 registration (a sodium fluoride [NaF]
                  positron emission tomography/computed tomography [PET/CT] is an acceptable
                  substitute); if the bone scan is suspicious, a plain x-ray, CT scan, NaF PET/CT
                  and/or MRI must be obtained to rule out metastasis

          -  Eastern Cooperative Oncology Group (ECOG) performance status of =< 1 within 90 days
             prior to step 1 registration

          -  Platelets >= 1 X 10^6 cells/mm^3 (100,000) based upon complete blood count (CBC)

          -  Hemoglobin >= 10.0 g/dl based upon CBC (Note: The use of transfusion or other
             intervention to achieve Hgb >= 10.0 g/dl is not allowed)

          -  Absolute neutrophil count greater than 1.5 x 10^9/L (1500)

          -  Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) < 1.5 x the upper
             limit of normal

          -  Total bilirubin normal unless history of Gilbert's syndrome

          -  The patient or a legally authorized representative must provide study-specific
             informed consent prior to step 1 registration

          -  Available surgical formalin-fixed paraffin-embedded (FFPE) specimen for genomic
             analysis on DECIPHER Genomic Resource Information Database (GRID) platform

        Exclusion Criteria:

          -  Definitive clinical or radiologic evidence of metastatic disease

          -  Prior invasive malignancy (except non-melanomatous skin cancer) unless disease free
             for a minimum of 2 years) Ta bladder cancer is not considered invasive

          -  Prior radiotherapy to the region of the study cancer that would result in overlap of
             radiation therapy fields

          -  Prior systemic chemotherapy for the study cancer; note that prior chemotherapy for a
             different cancer is allowable if completed more than two years prior to step 1
             registration; prior androgen deprivation is allowed

          -  Prior whole gland ablative therapy (i.e. cryoablation or high intensity focused
             ultrasound [HIFU]) for prostate cancer is allowed; prior focal HIFU or treatment for
             benign prostatic hypertrophy is allowed

          -  Prostatectomy performed greater than 365 days (1 year) prior to step 1 registration

          -  Severe and/or active co-morbidity defined as follows:

               -  History of inflammatory bowel disease

               -  History of active hepatitis B or C; blood tests are not required to determine if
                  the patient has had hepatitis B or C, unless the patient reports a history of
                  hepatitis

               -  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 step 1 registration

               -  Chronic obstructive pulmonary disease exacerbation or other respiratory illness
                  requiring hospitalization within 15 days of step 1 registration or precluding
                  study therapy at the time of step 1 registration

               -  Uncontrolled severe illness or medical condition (including uncontrolled
                  diabetes), which in the judgment of the treating physician would make the
                  administration of chemotherapy inadvisable

               -  Concurrent or planned treatment with strong inhibitors (e.g. ketoconazole,
                  clarithromycin, etcetera [etc]) or strong inducers (e.g. carbamazepine,
                  phenytoin, rifampin, phenobarbital, efavirenz, tipranavir, St. John's wort) of
                  cytochrome P450 3A4/5 (a one week wash-out period is necessary for patients who
                  are already on these treatments)

          -  Human immunodeficiency virus (HIV) positive with cluster of differentiation 4 (CD4)
             count < 200 cells/microliter; note that patients who are HIV positive are eligible,
             provided they are under treatment with highly active antiretroviral therapy (HAART)
             and have a CD4 count >= 200 cells/microliter within 30 days prior to step 1
             registration; note also that HIV testing is not required for eligibility for this
             protocol