Inclusion Criteria:

          -  Histologically confirmed prostate cancer

          -  PSA ≥ 0.1 after radical prostatectomy (value w/in 3 months of registration) AND at
             least 1 unfavorable risk factor listed below.

               -  Gleason 8-10

               -  PSA > 0.5

               -  Pathologically positive lymph nodes

               -  pT3 or pT4

               -  PSA doubling time (DT) < 10 months

               -  Negative margins

               -  Persistent PSA after RP (PSA never dropped below 0.1 after RP)

               -  Local/regional recurrence on imaging

               -  Decipher "High risk" (a Medicare-reimbursed test for risk of metastases after
                  prostatectomy)

          -  Candidate for salvage radiation and ADT treatment

          -  Written informed consent and HIPAA authorization for release of personal health
             information prior to registration. NOTE: HIPAA authorization may be included in the
             informed consent or obtained separately. Subject must have the ability to understand
             and willingness to sign the written informed consent document.

          -  18 ≤ Age ≤ 95 at the time of consent

          -  ECOG Performance Status ≤ 2 (Appendix A)

          -  Demonstrate adequate organ function as defined in the table below. All screening labs
             to be obtained within 3 months of registration.

          -  System Laboratory Value

          -  Hematological:

               -  Platelet count (plt) ≥ 100,000/ µL

               -  Hemoglobin (Hgb) ≥ 9 g/dL

               -  Absolute neutrophil count (ANC) ≥ 1000 cells/µL

          -  Renal:

             --GFR1 ≥ 45 mL/min

          -  Hepatic and Other:

               -  Bilirubin2 ≤ 1.5 × upper limit of normal (ULN)

               -  Aspartate aminotransferase (AST) ≤ 2.5 × ULN

               -  Alanine aminotransferase (ALT) ≤ 2.5 × ULN

               -  Serum Albumin > 3.0 g/dL

               -  Serum potassium ≥ 3.5 mmol/L

          -  Coagulation:

               -  International Normalized Ratio (INR)

               -  or Prothrombin Time (PT)

          -  Activated Partial Thromboplastin Time

               -  (aPTT) ≤ 1.5 × ULN (unless on prophylactic or therapeutic dosing with low
                  molecular weight heparin)

               -  Cockcroft-Gault formula will be used to calculate creatinine clearance (see study
                  procedure manual SPM)

               -  In subjects with Gilbert's syndrome, if total bilirubin is >1.5 × ULN, measure
                  direct and indirect bilirubin; if direct bilirubin is ≤1.5 × ULN, subject may be
                  eligible

          -  Agrees to use a condom (even men with vasectomies) and another effective method of
             birth control if he is having sex with a woman of childbearing potential OR agrees to
             use a condom if he is having sex with a woman who is pregnant while on study drug and
             for 3 months following the last dose of study drug.

          -  Must also agree not to donate sperm during the study and for 3 months after receiving
             the last dose of study drug.

          -  Ability to understand and comply with study procedures for the entire length of the
             study as determined by the site investigator or protocol designee

          -  Medications known to lower the seizure threshold (see list under prohibited meds) must
             be discontinued or substituted at least 4 weeks prior to study entry (Section 5.5)

          -  Use of CYP3A4 inhibitors or inducers and CYP2D6 substrates must be discontinued prior
             to study entry

          -  Able to swallow pills

        Exclusion Criteria:

          -  Use of post-prostatectomy ADT for > 30 continuous days prior to registration (ADT
             defined as use of GnRH agonist, with or without an anti-androgen). However, patients
             with testosterone recovery after post-prostatectomy ADT are eligible (testosterone
             recovery defined as total testosterone > 190 ng/dL) regardless of how long they have
             been on ADT.

          -  Prior pelvic radiation unless additional radiation can be safely delivered according
             to the treating physician

          -  PSA > 15 ng/mL in screening

          -  History of any of the following:

               -  Seizure or known condition that may predispose to seizure (e.g., prior stroke
                  within 1 year of randomization, brain arteriovenous malformation, Schwannoma,
                  meningioma, or other benign CNS or meningeal disease which may require treatment
                  with surgery or radiation therapy)

               -  Severe or unstable angina, myocardial infarction, symptomatic congestive heart
                  failure, arterial or venous thromboembolic events (e.g., pulmonary embolism,
                  cerebrovascular accident including transient ischemic attacks), or clinically
                  significant ventricular arrhythmias within 6 months prior to randomization

          -  Current evidence of any of the following:

               -  Uncontrolled hypertension

               -  Gastrointestinal disorder affecting absorption

               -  Active infection (e.g., human immunodeficiency virus [HIV] or viral hepatitis)

               -  Any chronic medical condition requiring a dose of corticosteroid higher than 10
                  mg prednisone/prednisolone once daily

               -  Any condition that, in the opinion of the site investigator, would preclude
                  participation in this study

               -  Moderate or severe hepatic impairment (Child Pugh Class B or C)

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to study drugs

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection, psychiatric illness or social situations that would limit compliance with
             study requirements

          -  Individuals with a history of another malignancy are not eligible if:

               -  the cancer is under active treatment or

               -  the cancer can be seen on radiology scans or

               -  if they are off cancer treatment but in the opinion of their oncologist have a
                  high risk of relapse within 5 years

          -  Confirmed bone metastases on imaging