Soy Isoflavones in Treating Patients Who Are Undergoing Radical Prostatectomy for Stage I or Stage II Adenocarcinoma of the Prostate

Soy Isoflavones in Treating Patients Who Are Undergoing Radical Prostatectomy for Stage I or Stage II Adenocarcinoma of the Prostate

RATIONALE: Chemoprevention therapy is the use of certain drugs to try to prevent or delay the development of early cancer. Soy isoflavones may be effective in delaying the development of early prostate cancer. PURPOSE: This randomized phase II trial is studying different regimens of soy isoflavones to compare how well they work in treating patients who are undergoing radical prostatectomy for stage I or stage II prostate cancer (adenocarcinoma).

OBJECTIVES: Compare blood/prostate biomarkers of oxidative stress and prostate cancer risk in patients with stage I or II adenocarcinoma of the prostate treated with 3 different dose levels of soy isoflavones before radical prostatectomy. Compare prostatic tissue biomarkers of proliferation and apoptosis in patients treated with these regimens. Determine the potential response, in terms of tumor and prostatic intraepithelial neoplasia grade and volume, extraprostatic extension, and serum prostate-specific antigen level, in patients treated with soy isoflavones and in those treated with placebo. Determine the safety of soy isoflavone supplementation in these patients. OUTLINE: This is a randomized, double-blind, placebo-controlled, parallel-group study. Patients are stratified according to tumor stage (T1c vs T2). Patients are randomized to 1 of 4 treatment arms. Arm I (control group): Patients receive oral placebo once daily. Arm II: Patients receive oral soy isoflavones and oral placebo once daily. Arm III: Patients receive a higher dose of oral soy isoflavones and oral placebo once daily. Arm IV: Patients receive a higher dose (higher than arm III) of oral soy isoflavones once daily. In all arms, treatment continues for 2-6 weeks (depending on the time from study entry to planned surgery) in the absence of unacceptable toxicity. All patients then undergo radical prostatectomy. Patients are followed at 1 week. PROJECTED ACCRUAL: A total of 100 patients (25 per treatment arm) will be accrued for this study within 12.5 months.

Arm II: Patients receive oral soy isoflavones (PTI G-2535) 150 mg genistein capsules + 3 placebo capsules by mouth daily for 3 weeks.

Arm III: Patients receive oral soy isoflavones (PTI G-2535) 300 mg genistein capsules + 2 placebo capsules by mouth daily for 3 weeks.

Arm IV: Arm III: Patients receive oral soy isoflavones (PTI G-2535) 600 mg genistein capsules by mouth daily for 3 weeks.

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate Stage T1c or T2 Disease confined to the prostate gland Planning to undergo radical prostatectomy within the next 3-4 weeks PATIENT CHARACTERISTICS: Age 18 and over Performance status Not specified Life expectancy Not specified Hematopoietic Not specified Hepatic ALT and AST less than 2 times upper limit of normal (ULN) Alkaline phosphatase less than 2 times ULN Renal Not specified Other Fertile patients must use effective barrier contraception Medically cleared for surgery No concurrent thyroid disease PRIOR CONCURRENT THERAPY: Biologic therapy No prior biological therapy for prostate cancer No concurrent biological agents Chemotherapy No prior chemotherapy for prostate cancer No concurrent chemotherapy Endocrine therapy No prior hormonal therapy for prostate cancer No concurrent thyroid hormone replacement medication No concurrent hormonal therapy Radiotherapy Not specified Surgery See Disease Characteristics Other At least 3 months since prior high-dose nutritional supplements No concurrent regular use (more than once weekly) of soy products greater than 50 g of soy protein or 50 mg of soy isoflavone No concurrent high-dose nutritional supplements Standard-dose single multivitamin tablet (e.g., Centrum™) allowed No concurrent herbs No concurrent soy foods No other concurrent isoflavone supplements No other concurrent antineoplastic agents