RATIONALE: Antineoplastons are naturally occurring substances that may also be made in the laboratory. Antineoplastons may inhibit the growth of cancer cells.

PURPOSE: This phase II trial is studying how well antineoplaston therapy works in treating patients with stage III or stage IV prostate cancer.

OBJECTIVES:

• Determine the antitumor activity of antineoplastons A10 and AS2-1 capsules in combination with total androgen blockade in patients with localized, regional or metastatic adenocarcinoma of the prostate by determining the proportion of patients who experience an objective tumor response.
• Evaluate the adverse effects of and tolerance to this regimen in these patients.

OUTLINE: This is an open-label study.

Patients receive gradually escalating doses of antineoplastons A10 and AS2-1 capsules orally 6-7 times daily until the maximum tolerated dose is reached. Treatment continues for at least 3 months in the absence of disease progression or unacceptable toxicity. Concurrently, patients continue hormonal therapy with flutamide, leuprolide, or bicalutamide at the same dose as before beginning antineoplaston therapy.

Tumors are measured every 4 months for 2 years, every 6 months for 2 years, and then annually for 2 years.

PROJECTED ACCRUAL: A total of 50 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically proven localized, regional, or metastatic adenocarcinoma of the prostate
• Progressive disease during prior hormonal therapy (both antiandrogen and gonadotropin-releasing hormone) and must continue hormonal therapy
• Measurable tumors or tumor markers
• Bone metastases allowed

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• At least 3 months

Hematopoietic:

• WBC at least 3,000/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• No hepatic failure
• Bilirubin no greater than 2.5 mg/dL
• SGOT no greater than 2 times normal

Renal:

• No chronic renal failure
• 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

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 infections or fever
• No other prior or concurrent second malignancy within the past 2 years

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 4 weeks since prior biologic therapy and recovered

Chemotherapy:

• At least 4 weeks since prior chemotherapy and recovered

Endocrine therapy:

• See Disease Characteristics

Radiotherapy:

• At least 4 weeks since prior radiotherapy and recovered

Surgery:

• Not specified

Other:

• At least 4 weeks since prior investigational clinical trial
• No other concurrent treatment for metastatic prostate cancer