Pomegranate Extract in Treating Patients With Rising Prostate-Specific Antigen Levels After Surgery or Radiation Therapy for Localized Prostate Cancer

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate Must have completed prior surgery, cryotherapy, or radiotherapy for the primary tumor Documented rising prostate-specific antigen (PSA) Absolute level of PSA > 0.2 ng/mL after surgery Absolute level of PSA > 1.0 ng/mL after radiation or cryotherapy Absolute level of PSA ≥ 0.4 ng/mL after multiple treatment modalities (e.g., surgery with radiotherapy or radiotherapy with cryotherapy) PSA must be ≥ 100% above best nadir achieved PSA doubling time > 3 months or ≤ 24 months Patients must have ≥ 3 rising PSA time points above the minimum nadir achieved over ≥ 6 months The interval between PSA time points must be > 2 weeks PSA ≤ 7.0 ng/mL Patients who underwent radical prostatectomy and never achieved undetectable serum PSA after surgery are not eligible Gleason score ≤ 7 No histologically positive lymph nodes No evidence of metastatic disease by physical examination, CT scan, or bone scan PATIENT CHARACTERISTICS: Life expectancy ≥ 6 months ECOG performance status 0 or 1 No significant concomitant medical or psychiatric conditions that would limit study compliance No known allergies to pomegranate extract No known diabetes with hemoglobin A_1c level > 7.0% in the past 3 months Diabetic patients entering study who have not had hemoglobin A_1c level measured in the past 3 months must have levels measured at study initiation No clinically abnormal laboratory values > 2 times the upper limit of normal PRIOR CONCURRENT THERAPY: See Disease Characteristics More than 4 weeks since prior and no concurrent experimental drugs, high-dose steroids, or other cancer treatment No hormonal therapy, with the exception of neoadjuvant androgen-deprivation therapy (ADT), prior to or concurrent with primary therapy Patients who received prior neoadjuvant ADT must have serum testosterone ≥ 150 ng/dL No prior or concurrent hormonal therapy for rising PSA after primary therapy for prostate cancer No finasteride or dutasteride at any time point after primary therapy and during study therapy No other concurrent commercial pomegranate products No other concurrent systemic or local therapy for prostate cancer Concurrent dietary/herbal supplements (e.g., saw palmetto or selenium) allowed provided dose has been stable for ≥ 2 months prior to study entry and there are no plans to change or stop the supplements during study therapy