CLINICAL TRIAL / NCT01436968

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