Effect of soy protein isolate supplementation on biochemical recurrence of prostate cancer after radical prostatectomy: A randomized trial

Maarten C. Bosland, Ikuko Kato, Anne Zeleniuch-Jacquotte, Joanne Schmoll, Erika Enk Rueter, Jonathan Melamed, Max Xiangtian Kong, Virgilia Macias, Andre Kajdacsy-Balla, L. H. Lumey, Hui Xie, Weihua Gao, Paul Walden, Herbert Lepor, Samir S. Taneja, Carla Randolph, Michael J. Schlicht, Hiroko Meserve-Watanabe, Ryan J. Deaton, Joanne A. Davies

    Research output: Contribution to journalArticle

    Abstract

    IMPORTANCE: Soy consumption has been suggested to reduce risk or recurrence of prostate cancer, but this has not been tested in a randomized trial with prostate cancer as the end point. OBJECTIVE: To determine whether daily consumption of a soy protein isolate supplement for 2 years reduces the rate of biochemical recurrence of prostate cancer after radical prostatectomy or delays such recurrence. DESIGN, SETTING, AND PARTICIPANTS: Randomized, double-blind trial conducted from July 1997 to May 2010 at 7 US centers comparing daily consumption of a soy protein supplement vs placebo in 177 men at high risk of recurrence after radical prostatectomy for prostate cancer. Supplement intervention was started within 4 months after surgery and continued for up to 2 years, with prostate-specific antigen (PSA) measurements made at 2-month intervals in the first year and every 3 months thereafter. INTERVENTION: Participants were randomized to receive a daily serving of a beverage powder containing 20 g of protein in the form of either soy protein isolate (n=87) or, as placebo, calcium caseinate (n=90). MAIN OUTCOMES AND MEASURES: Biochemical recurrence rate of prostate cancer (defined as development of a PSA level of ≥0.07 ng/mL) over the first 2 years following randomization and time to recurrence. RESULTS: The trial was stopped early for lack of treatment effects at a planned interim analysis with 81 evaluable participants in the intervention group and 78 in the placebo group. Overall, 28.3%of participants developed biochemical recurrence within 2 years of entering the trial (close to the a priori predicted recurrence rate of 30%). Among these, 22 (27.2%) occurred in the intervention group and 23 (29.5%) in the placebo group. The resulting hazard ratio for active treatment was 0.96 (95%CI, 0.53-1.72; log-rank P = .89). Adherence was greater than 90% and there were no apparent adverse events related to supplementation. CONCLUSION AND RELEVANCE: Daily consumption of a beverage powder supplement containing soy protein isolate for 2 years following radical prostatectomy did not reduce biochemical recurrence of prostate cancer in men at high risk of PSA failure. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00765479.

    Original languageEnglish (US)
    Pages (from-to)170-178
    Number of pages9
    JournalJAMA - Journal of the American Medical Association
    Volume310
    Issue number2
    DOIs
    StatePublished - 2013

    ASJC Scopus subject areas

    • Medicine(all)

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    Bosland, M. C., Kato, I., Zeleniuch-Jacquotte, A., Schmoll, J., Enk Rueter, E., Melamed, J., Kong, M. X., Macias, V., Kajdacsy-Balla, A., Lumey, L. H., Xie, H., Gao, W., Walden, P., Lepor, H., Taneja, S. S., Randolph, C., Schlicht, M. J., Meserve-Watanabe, H., Deaton, R. J., & Davies, J. A. (2013). Effect of soy protein isolate supplementation on biochemical recurrence of prostate cancer after radical prostatectomy: A randomized trial. JAMA - Journal of the American Medical Association, 310(2), 170-178. https://doi.org/10.1001/jama.2013.7842