Genistein in Treating Patients With Localized Prostate Cancer Who Are Planning to Undergo Radical Prostatectomy

DISEASE CHARACTERISTICS: Diagnosis of localized prostate cancer Diagnosed within the past 6 months T1 or T2 disease Gleason score 5-8 Prostate-specific antigen no greater than 20 ng/mL Radical prostatectomy planned PATIENT CHARACTERISTICS: Age 18 and over Performance status ECOG 0-1 Life expectancy More than 2 years Hematopoietic Hemoglobin greater than 9.0 g/dL Platelet count greater than 100,000/mm^3 Absolute neutrophil count greater than 1,000/mm^3 Hepatic SGPT and SGOT less than 3 times normal Bilirubin less than 3 mg/dL (less than 1.5 times normal) (patients with an elevated bilirubin due to a familial defect in bilirubin metabolism will be considered on an individual basis) Renal Creatinine less than 2.0 mg/dL Cardiovascular No venous thrombosis within the past year Other Patients must use effective barrier contraception No other medical condition that would preclude study therapy No known soy intolerance PRIOR CONCURRENT THERAPY: Biologic therapy Not specified Chemotherapy Not specified Endocrine therapy No concurrent hormonal therapy for prostate cancer Radiotherapy Not specified Surgery See Disease Characteristics Other No concurrent soy supplements No concurrent foods high in genistein No concurrent active therapy for neoplastic disorders