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

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

Status

Completed

Phases

Phase 2

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00031746

Enrollment

Registered

2003-01-27

Start date

2000-02-29

Completion date

2006-06-30

Last updated

2016-07-19

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Prostate Cancer

Keywords

prostate cancer

Brief summary

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

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.

Interventions

DIETARY_SUPPLEMENTsoy protein isolate

25 mg daily

DIETARY_SUPPLEMENTcasein proteins

25 mg daily

Study design

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

PREVENTION

Masking

DOUBLE (Subject, Caregiver)

Eligibility

Sex/Gender

MALE

Age

50 Years to No maximum

Healthy volunteers

Inclusion criteria

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

Design outcomes

Primary

Measure	Time frame
Reduction of prostatic cellular proliferation rates by 50% as measured by Ki-67	12 months

Countries

United States

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026