DISEASE CHARACTERISTICS: Histologically confirmed progressive metastatic or progressive regional nodal adenocarcinoma of the prostate Regression of tumor following hormone therapy If on antiandrogen therapy, must fail to respond to withdrawal or have progressive disease following withdrawal of antiandrogen No CNS disease

PATIENT CHARACTERISTICS: Age: Not specified Performance status: WCCC 0-2 Life expectancy: At least 3 months Hematopoietic: WBC at least 3000/mm3 Absolute neutrophil count at least 1200/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 8 g/dL Hepatic: Bilirubin no greater than 1.5 mg/dL SGOT no greater than 2.5 times normal Renal: Creatinine no greater than 1.5 times upper limit of normal Other: At least 5 years since prior malignancy other than: Inactive nonmelanoma skin cancer Adequately treated stage I or II cancer in complete remission No other serious illness No spinal cord compression symptoms

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Prior chemotherapy required Endocrine therapy: Failed one secondary hormonal manipulation for metastatic disease Concurrent testicular androgen suppression (LHRH) allowed No concurrent hormonal therapy other than LHRH agonist At least 4 weeks since antiandrogen treatment in order to evaluate for response withdrawal Radiotherapy: At least 4 weeks since prior radiation therapy No prior strontium therapy Surgery: No prior orchiectomy Other: No concurrent cholesterol lowering agents No concurrent supplemental vitamins No concurrent antioxidants