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.

Does equol production determine soy endocrine effects?

“…This is important since prostate cancer pathophysiology is associated with the andropause when there is a rise in the oestrogen to androgens ratio and oestrogen has been associated with carcinogenesis of the prostate [127]. Conversely, Kumar et al did not demonstrate a significant effect on total oestrodial (among other hormones) following consumption of 80 mg of isoflavones by men with early stage prostate cancer for 12 weeks [128].…”

Multi-targeted therapy of cancer by genistein

“…A phase II randomized, placebo-controlled clinical trial using purified isoflavones in modulating steroid hormones in patients with localized prostate cancer has been reported recently [144]. 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.…”

“…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, suggesting the need to explore other potential mechanisms by which prolonged and consistent purified isoflavone consumption may modulate prostate cancer risk [144].…”

Prostate Cancer Prevention: Agent Development Strategies

“…This population may also provide a useful cohort in which to evaluate the usefulness of genomics and proteomics to predict the natural history of this heterogeneous disease. Pilot studies of soy isoflavones, lycopene, omega-3 fatty acids, and selenium have recently been completed in men with low-risk prostate cancer being followed with active surveillance (Chan et al 2011;Kumar et al 2007;Stratton et al 2010). An NCIsupported randomized clinical trial of pomegranate fruit extract in this population is currently pending activation.…”