RATIONALE: A low-fat, high-fiber diet that includes soy protein may prevent disease progression in patients with hormone-refractory prostate cancer. Nutrition counseling may help motivate patients to follow this diet.

PURPOSE: Randomized phase I trial to study the effectiveness of behavior-based dietary interventions, such as receiving nutrition counseling, in helping patients who have hormone-refractory prostate cancer follow a low-fat, high-fiber, soy-supplemented diet.

OBJECTIVES:

• Determine whether a behavior-based dietary intervention can motivate patients with hormone-refractory prostate cancer to adopt and maintain a dietary pattern that includes < 20% of energy from fat, > 25 g of fiber, and 80 g of soy protein powder.
• Compare bioavailable levels of testosterone in patients treated with a behavior-based dietary intervention vs observation only.
• Determine whether this dietary intervention decreases or stabilizes a rising serum prostate-specific antigen level in these patients.
• Determine whether this dietary intervention improves disease-specific survival, mediated by reduced bioavailable levels of testosterone, in these patients.
• Determine the impact of a positive intervention outcome on androgen receptors in patients treated with this dietary intervention.

OUTLINE: This is a randomized, controlled, pilot, multicenter study. Patients are randomized to 1 of 2 treatment arms.

All patients receive nutritional counseling on a healthy diet. Patients also keep a food diary during study participation.

• Arm I (dietary intervention): Patients receive dietary intervention comprising nutritional counseling on a low-fat, high-fiber, soy supplemented diet and behavior-based activities, such as goal-setting, contracting, and stimulus control, once weekly for 6 weeks, every 3 weeks for 33 weeks, and then at weeks 44, 48, and 52. Treatment continues in the absence of disease progression or unacceptable toxicity.
• Arm II (observation): Patients undergo observation every 6 weeks for 36 weeks and then every 8 weeks for 18 weeks.

PROJECTED ACCRUAL: A total of 92 patients (46 per treatment arm) will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • No small cell component

• No histologically confirmed and/or demonstrable metastatic or locally recurrent disease by bone scan, chest x-ray, computed tomography (CT) scan, or transrectal ultrasound

  • No clinical symptoms within the past 90 days

• Documented biochemical failure after radical prostatectomy

  • Prostate-specific antigen must have initially nadired to an undetectable level (< 0.1 ng/mL) after prostatectomy AND is currently rising (0.3-40.0 ng/mL)

• Serum testosterone > 100 ng/dL

PATIENT CHARACTERISTICS:

Age

• Any age

Performance status

• Zubrod 0-1

Life expectancy

• At least 1 year

Hematopoietic

• Not specified

Hepatic

• Not specified

Renal

• Not specified

Other

• No known allergic reactions to milk or soy products

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• More than 1 year since prior chemotherapy

Endocrine therapy

• More than 1 year since prior hormonal therapy

Radiotherapy

• Not specified

Surgery

• See Disease Characteristics