Soy Protein Supplement in Preventing Prostate Cancer in Patients With Elevated Prostate-Specific Antigen Levels

Study Overview
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Brief Summary
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RATIONALE: Soy protein supplement may prevent or delay the development of prostate cancer in patients who have elevated prostate-specific antigen (PSA) levels. PURPOSE: Randomized phase II trial to determine the effectiveness of soy protein supplement in preventing prostate cancer in patients who have elevated PSA levels.

Detailed Description
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OBJECTIVES: Compare the reduction in the rate of prostatic cellular proliferation in patients with an elevated PSA (5 to 10 ng/mL) and a negative biopsy for prostate cancer when treated with daily soy protein supplements vs placebo. Compare the effect of these regimens on additional biomarkers of prostate cancer (PSA, high-grade prostate intraepithelial neoplasia, induction of apoptosis, sex steroid receptor expression, and loss of glutathione S-transferase-pi) in these patients. Compare the effect of these regimens on quality of life, including urinary and sexual function, in these patients. OUTLINE: This is a randomized, double-blind, placebo-controlled, multicenter study. Patients are stratified according to race (Caucasian vs African American). After 2 weeks of daily oral placebo, patients are randomized to 1 of 2 arms. Arm I: Patients receive oral soy protein supplement daily for 12 months. Arm II: Patients receive oral placebo daily for 12 months. Quality of life is assessed at baseline and at 6 and 12 months. PROJECTED ACCRUAL: A total of 160 patients (80 per arm) will be accrued for this study within 12 months.

Official Title
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Effects of Dietary Soy on Biomarkers of Prostate Cancer: A Prospective Phase II Study

Conditions
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Prostate Cancer

Intervention / Treatment
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* Dietary Supplement: soy protein isolate
* Dietary Supplement: casein proteins


Participation Criteria
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Eligibility Criteria
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DISEASE CHARACTERISTICS: Histologically confirmed absence of prostate cancer Atypical adenomatous hyperplasia or prostatic intraepithelial neoplasia (high-grade or low-grade) allowed Abnormal baseline transrectal ultrasound and digital rectal exam allowed Biopsy may be before or after study entry, but must be within the past 90 days PSA 5-10 ng/mL PATIENT CHARACTERISTICS: Age: 50 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: No known allergy to soy protein or milk protein No invasive cancer within the past 5 years except non-melanoma skin cancer PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: No prior hormonal therapy No prior finasteride No concurrent hormonal therapy No concurrent finasteride Radiotherapy: Not specified Surgery: At least 6 months since prior transurethral resection of the prostate No prior orchiectomy No concurrent orchiectomy Other: No other concurrent soy products

Ages Eligible for Study
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Minimum Age: 50 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: soy protein + isoflavones<br> | Dietary Supplement: soy protein isolate<br>* 25 mg daily<br>|
| Active Comparator: casein proteins<br> | Dietary Supplement: casein proteins<br>* 25 mg daily<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Reduction of prostatic cellular proliferation rates by 50% as measured by Ki-67 |  | 12 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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prostate cancer