Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven stage III or IV adenocarcinoma of the prostate not potentially
curable by surgery or radiotherapy

- Measurable tumors or tumor markers

- No response to antiandrogen withdrawal

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 60-100%

Life expectancy:

- At least 3 months

Hematopoietic:

- WBC at least 3000/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 2.5 mg/dL

- SGOT no greater than 2 times normal

- No hepatic failure

Renal:

- BUN less than 60 mg/dL

- Creatinine no greater than 2.5 mg/dL OR

- Creatinine clearance greater than 60 mL/min

- Blood ammonia normal

- No chronic renal failure

Cardiovascular:

- No severe heart disease

Pulmonary:

- No severe lung disease

Other:

- Fertile patients must use effective contraception during and for 4 weeks after study
participation

- No serious active infection or fever

- No other concurrent serious disease

- No other prior or concurrent malignancy within the past 2 years

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 4 weeks since prior immunotherapy and recovered

Chemotherapy:

- At least 4 weeks since prior chemotherapy and recovered

Endocrine therapy:

- At least 4 weeks since prior hormonal therapy and recovered

- Prior corticosteroids for at least 2 months allowed, but must be on stable or
decreasing dose during study participation

Radiotherapy:

- See Disease Characteristics

- At least 4 weeks since prior radiotherapy and recovered

Surgery:

- See Disease Characteristics

- At least 4 weeks since prior surgery and recovered

Other:

- At least 4 weeks since prior experimental clinical trial

- No other concurrent therapy for metastatic disease