Exemestane With or Without Bicalutamide in Treating Patients With Stage IV Prostate Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed stage IV adenocarcinoma of the prostate Documented disease progression based on prostate-specific antigen (PSA) progression during first-line androgen suppression (luteinizing hormone-releasing hormone agonist or orchiectomy) PSA progression is defined by the following: Interval of at least 1 week between reference value (time point value 1) and the next PSA level (time point value 2) PSA at time point value 3 is greater than PSA at time point value 2 OR PSA at time point value 3 is not greater than PSA at time point value 2, but PSA at time point value 4 is greater than PSA at time point value 2 PSA at least 5 ng/mL Must continue primary androgen suppression if no prior surgical castration No known leptomeningeal or brain metastases PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-2 Life expectancy: Not specified Hematopoietic: WBC at least 3,500/mm^3 Neutrophil count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) AST and ALT no greater than 2.5 times ULN Renal: Creatinine no greater than 1.5 times ULN Other: No acute concurrent severe infection No other concurrent significant disease that would preclude study therapy No other malignancy within the past 5 years except curatively treated basal cell or squamous cell skin cancer PRIOR CONCURRENT THERAPY: Biologic therapy: No prior antibody or gene therapy Chemotherapy: No prior cytostatic agents Endocrine therapy: See Disease Characteristics No prior estramustine No prior antiandrogens (e.g., bicalutamide) No concurrent estrogen-containing medicine Radiotherapy: More than 4 weeks since prior radiotherapy No concurrent radiotherapy to more than 1 field Surgery: See Disease Characteristics Other: At least 4 weeks since prior investigational drugs