DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate that is stage D2 Measurable or evaluable disease required with at least one of the following: At least 7 bone lesions Visceral involvement No more than 50% replacement of liver by tumor No clinical suspicion of brain metastases No spinal cord compression

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 (ECOG 3 allowed if increase due only to pain) Life expectancy: At least 3 months Hematopoietic: (within 2 weeks prior to entry) WBC at least 3,000 AGC at least 1,500 Platelets at least 100,000 Hemoglobin at least 9.0 g/dL Hepatic: (within 2 weeks prior to entry) Bilirubin no greater than 2 times normal AST and ALT no greater than 2 times normal PT and PTT normal Albumin at least 3.0 g/dL Renal: Creatinine no greater than 2 mg/dL Creatinine clearance at least 60 mL/min BUN no greater than twice normal Cardiovascular: No myocardial infarction within 6 months No NYHA class III/IV status No history of thromboembolic or hemorrhagic cerebrovascular accident No disseminated intravascular coagulation No anticoagulant therapy (aspirin allowed for other uses) Other: No active bacterial infection No HIV or hepatitis B infection No other malignancy within the past 5 years except curatively treated nonmelanoma skin cancer or carcinoma in situ cancer of any site

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biological response modifier therapy Chemotherapy: No prior chemotherapy (including suramin) Endocrine therapy: At least 1 year since any adjuvant or neoadjuvant hormone therapy No more than 4 months of therapy as part of initial prostate cancer therapy Prior finasteride for benign prostatic hypertrophy allowed No systemic steroids other than hydrocortisone (steroid inhalers allowed) Radiotherapy: At least 4 weeks since radiotherapy (90 days since strontium) Surgery: Recovered from prior surgery