A Phase II Randomized, Placebo-Controlled Clinical Trial of Purified Isoflavones in Modulating Steroid Hormones in Men Diagnosed With Localized Prostate Cancer

Abstract

Our purpose was to evaluate the safety and effectiveness of purified isoflavones in producing an increase in plasma isoflavones and a corresponding change in serum sex hormone binding globulin (SHBG) and steroid hormone levels in men diagnosed with early stage prostate cancer. In this Phase II randomized, double-blinded, placebo-controlled trial, 53 prostate cancer patients with a Gleason score of 6 or below were supplemented with 80 mg purified isoflavones or placebo for 12 weeks. Changes in plasma isoflavones, serum steroid hormones, and safety markers were analyzed from baseline to 12 wk. A total of 50 subjects completed the study. Although significant increases in plasma isoflavones (P < 0.001) was observed with no clinical toxicity, the corresponding modulation of serum SHBG, total estradiol, and testosterone in the isoflavone-treated group compared to men receiving placebo was nonsignificant. Increasing plasma isoflavones failed to produce a corresponding modulation of serum steroid hormone levels in men with localized prostate cancer. The study establishes the need to explore other potential mechanisms by which prolonged and consistent purified isoflavone consumption may modulate prostate cancer risk.

Acknowledgments and Notes

The research study was funded by the National Institute of Health—National Cancer Institute U10 CA81920. To date, the results of this study in part or as a whole has not been reported nor presented elsewhere.

Notes

a: P compared the change between 2 groups by Satterthwaite t-test.

a: Abbreviation is as follows: SHBG, sex hormone binding globulin.

b: P, paired t-test comparing mean at baseline with at week 12 by group.

c: P, 2-sided P values calculated for testing the difference in changes between treatment groupand the placebo group by pooled t-test or by Satterthwaite t-test if equal variance does not meet.