Inclusion Criteria include:

          -  Localized prostate cancer meeting the NCCN criteria of Intermediate Risk or patients
             having only one NCCN high-risk feature

               -  NCCN Intermediate Risk is defined as having at least one of the following: PSA
                  10-20 ng/ml, Gleason score =7, T2b-T2c

               -  High Risk with a single high risk feature is defined as having only one of the
                  following: PSA>20 ng/ml, Gleason score 8-10, or T3a

               -  Excluded are those in the following risk groups: Low risk; High risk with more
                  than 1 high risk factor; Locally advanced/very high risk=T3b-T4; Metastatic: N1
                  or M1

          -  Planning to undergo standard prostate-only external beam radiation therapy

          -  ECOG Performance Status 0-2

        Exclusion Criteria include:

          -  Liver disease, including known cirrhosis or active hepatitis

          -  Patients on systemic corticosteroids (>10mg prednisone per day) or other
             immunosuppressive drugs

          -  Known HIV+ patients

          -  Regional lymph node involvement or distant metastases

          -  Patients planning to receive whole pelvic irradiation

          -  Prior treatment for prostate cancer, except TURP or ADT. For ADT, it may only be given
             for a maximum of 6 months

          -  Patients who had or plan to have orchiectomy as the form of hormonal ablation

          -  Known sensitivity or allergic reactions to acyclovir or valacyclovir