Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of androgen-independent prostate cancer

- Asymptomatic metastatic disease

- Unlikely to become symptomatic within the next 4 months

- No bone pain, shortness of breath, fatigue, or urinary symptoms directly
attributable to prostate cancer

- Radiologic, physically palpable, and/or biochemical evidence of tumor progression
after prior orchiectomy OR during treatment with a luteinizing hormone-releasing
hormone (LHRH) agonist OR after initiation of another hormonal agent

- Sustained prostate-specific antigen (PSA) elevation, defined by the following:

- PSA greater than 5 ng/mL

- At least 2 consecutive increases in PSA at least 1 week apart

- Sustained increase in PSA at least 4 weeks after discontinuation of prior
flutamide (or other antiandrogen therapy) or megestrol AND at least 6 weeks
after discontinuation of prior bicalutamide

- No known CNS metastases or carcinomatous meningitis

PATIENT CHARACTERISTICS:

Age

- 18 and over

Performance status

- ECOG 0-2

Life expectancy

- At least 12 weeks

Hematopoietic

- Not specified

Hepatic

- Bilirubin no greater than 1.5 mg/dL* NOTE: *Includes patients with liver involvement
secondary to tumor

Renal

- See Disease Characteristics

- Creatinine no greater than 2 times upper limit of normal

Pulmonary

- See Disease Characteristics

Other

- No other malignancy within the past 5 years except basal cell skin cancer

- No medical or psychiatric condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

- More than 4 weeks since prior immunotherapy

Chemotherapy

- More than 4 weeks since prior chemotherapy

- No concurrent chemotherapy

Endocrine therapy

- See Disease Characteristics

- More than 4 weeks since prior hormonal therapy (other than an LHRH agonist)

- No concurrent corticosteroids

- No concurrent progestational agents

- No concurrent new hormonal therapy

Radiotherapy

- No concurrent radiotherapy, including radiotherapy for new bone disease

Surgery

- See Disease Characteristics

Other

- More than 4 weeks since other prior anticancer therapy

- No other concurrent investigational anticancer agents

- No other concurrent alternative medicine therapies (e.g., saw palmetto or PC-SPES)