Soy Protein in Preventing Recurrent Cancer in Patients Who Have Undergone Surgery for Stage II Prostate Cancer

University of Illinois at Chicago284 enrolled

Overview

RATIONALE: Soy protein may help prevent prostate cancer recurrence in patients who have undergone surgery for prostate cancer. PURPOSE: This randomized phase II/III trial is studying how well soy protein works and compares it to a placebo in preventing recurrent cancer in patients who have undergone surgery for stage II prostate cancer.

OBJECTIVES: * Determine whether soy protein isolate reduces the PSA failure rate and time to PSA failure within 2 years following radical prostatectomy in patients who are at high risk for prostate cancer recurrence. * Determine the effects of soy protein isolate on intermediate biomarkers of steroid hormone axis (testosterone, estradiol, and SHBG) and thyroid activity (T3 and T4). * Determine the effects of soy protein isolate on intermediate biomarkers of apoptosis (soluble Fas and Fas-ligand), angiogenesis (VEGF and bFGF), antioxidant activity (8-isoprostanes), and IGF axis (IGF-1 and IGFBP-3). * Compare patients who are equol producers to those who are non-producers. OUTLINE: This is a multicenter study. Patients are stratified according to hospital/clinic site (NYU vs UIC or Jesse Brown VA Medical Center vs other sites), number of high-risk characteristics (1 vs \> 1), and race (African American vs non-African American \[i.e., non-Hispanic White, Hispanic, Asian, and other\]). Patients are randomized to 1 of 2 treatment arms. * Arm I: Patients receive an oral soy protein isolate beverage once daily. * Arm II: Patients receive an oral casein placebo beverage once daily. Treatment in both arms continues for up to 2 years in the absence of disease progression or unacceptable toxicity. Blood samples are collected periodically for biomarker laboratory studies. Samples are analyzed to measure PSA levels by Tosoh PSA assay; cholesterol levels; isoflavone and equol concentrations by HPLC and ESA; and indicators of steroid hormone axis (testosterone, estradiol, and SHBG), indicators of thyroid activity (T3 and T4), indicators of apoptosis (soluble Fas and Fas-ligand), indicators of angiogenesis (VEGF and bFGF), indicators of oxidative stress (8-isoprostanes), and indicators of IGF axis (IGF-1 and IGFBP-3) by ELISA.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Enrollment

284

Conditions

Prostate Cancer

Interventions

soy protein isolateDIETARY_SUPPLEMENT

Given orally

placeboOTHER

Given orally

Eligibility

Sex: MALEMin age: 40 YearsMax age: 75 Years

Medical Language ↔ Plain English

DISEASE CHARACTERISTICS: * Diagnosis of prostate cancer * Clinically localized (T1c or T2) disease * At high risk for recurrence, as defined by ≥ 1 of the following: * Preoperative PSA \> 20.0 ng/mL * Seminal vesicle invasion * Extracapsular extension (excluding the bladder neck) * Positive surgical margins (excluding apical margins) * Micrometastases in any removed pelvic lymph nodes * Final Gleason score of ≥ 8 * Must have undergone radical prostatectomy for prostate cancer within the past 4 months * Must have an undetectable PSA (\< 0.07 ng/mL) at baseline, as measured by Tosoh PSA assay * No clinical evidence of locally recurrent or metastatic disease PATIENT CHARACTERISTICS: * No significant intake of soy (i.e., more than once a week) at baseline including, but not limited to, any of the following: * Vegetarians who regularly consume soy products (e.g., tofu) * Individuals with customary Asian dietary habits, including regular intake of soy products * Individuals who use soy-based milk replacements * No anemia, iron deficiency problems, or subclinical iron deficiency at baseline * No diabetes * No thyroid disease * No requirement for a sodium-free diet * No substantive tendency to be constipated (i.e., ≥ grade 2 constipation experienced regularly) * No medical problem that would preclude the consumption of the soy containing beverage powder, including allergies against soy (or milk protein) * No concurrent major disease, including major mental disease or major substance abuse problems * No significant side effects from medication PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No concurrent radiotherapy or hormonal therapy * No other concurrent adjuvant therapy for prostate cancer

Locations (1)

University of Illinois Cancer Center

Chicago, Illinois, United States

Outcomes

Primary Outcomes

Two-year PSA failure rate (as surrogate for recurrence)

Time to PSA failure

Secondary Outcomes

Isoflavone uptake or compliance as measured by serum isoflavone concentration

Serum total cholesterol levels

Steroid hormone axis as measured by serum testosterone, estradiol, and SHBG levels

Thyroid activity as measured by serum T3 and T4 levels

Apoptotic activity as measured by serum soluble Fas and Fas-ligand levels

Angiogenesis as measured by serum VEGF and bFGF levels

Oxidative stress as measured by serum 8-isoprostane levels

IGF axis as measured by serum IGF-1 and IGFBP-3 levels

Equol production as measured by serum equol concentration

Data from ClinicalTrials.gov

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