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

This study has been completed.
National Cancer Institute (NCI)
Information provided by (Responsible Party):
Alliance for Clinical Trials in Oncology Identifier:
First received: March 8, 2002
Last updated: July 15, 2016
Last verified: July 2016

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.

Condition Intervention Phase
Prostate Cancer
Dietary Supplement: soy protein isolate
Dietary Supplement: casein proteins
Phase 2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Care Provider)
Primary Purpose: Prevention
Official Title: Effects of Dietary Soy on Biomarkers of Prostate Cancer: A Prospective Phase II Study

Resource links provided by NLM:

Further study details as provided by Alliance for Clinical Trials in Oncology:

Primary Outcome Measures:
  • Reduction of prostatic cellular proliferation rates by 50% as measured by Ki-67 [ Time Frame: 12 months ]

Enrollment: 26
Study Start Date: February 2000
Study Completion Date: June 2006
Primary Completion Date: June 2006 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: soy protein + isoflavones Dietary Supplement: soy protein isolate
25 mg daily
Active Comparator: casein proteins Dietary Supplement: casein proteins
25 mg daily

Detailed Description:


  • 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.


Ages Eligible for Study:   50 Years and older   (Adult, Senior)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   No


  • 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



  • 50 and over

Performance status:

  • ECOG 0-2

Life expectancy:

  • Not specified


  • Not specified


  • Not specified


  • Not specified


  • No known allergy to soy protein or milk protein
  • No invasive cancer within the past 5 years except non-melanoma skin cancer


Biologic therapy:

  • Not specified


  • Not specified

Endocrine therapy:

  • No prior hormonal therapy
  • No prior finasteride
  • No concurrent hormonal therapy
  • No concurrent finasteride


  • Not specified


  • At least 6 months since prior transurethral resection of the prostate
  • No prior orchiectomy
  • No concurrent orchiectomy


  • No other concurrent soy products
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00031746

United States, District of Columbia
Walter Reed Army Medical Center
Washington, District of Columbia, United States, 20307-5001
United States, New York
CCOP - Hematology-Oncology Associates of Central New York
Syracuse, New York, United States, 13057
Community General Hospital of Greater Syracuse
Syracuse, New York, United States, 13215
United States, North Carolina
Wake Forest University Comprehensive Cancer Center
Winston-Salem, North Carolina, United States, 27157-1096
United States, Ohio
Arthur G. James Cancer Hospital and Solove Research Institute at Ohio State University
Columbus, Ohio, United States, 43210-1240
Sponsors and Collaborators
Alliance for Clinical Trials in Oncology
National Cancer Institute (NCI)
Study Chair: James L. Mohler, MD Roswell Park Cancer Institute
  More Information

Responsible Party: Alliance for Clinical Trials in Oncology Identifier: NCT00031746     History of Changes
Other Study ID Numbers: CALGB-79806
U10CA076001 ( US NIH Grant/Contract Award Number )
CDR0000069221 ( Registry Identifier: NCI Physicians Data Query )
Study First Received: March 8, 2002
Last Updated: July 15, 2016

Keywords provided by Alliance for Clinical Trials in Oncology:
prostate cancer

Additional relevant MeSH terms:
Prostatic Neoplasms
Genital Neoplasms, Male
Urogenital Neoplasms
Neoplasms by Site
Genital Diseases, Male
Prostatic Diseases
Chelating Agents
Sequestering Agents
Molecular Mechanisms of Pharmacological Action processed this record on April 21, 2017