For men at high risk of biochemical recurrence after radical prostatectomy (RP), daily consumption of a soy protein supplement is not associated with a reduction in the risk of recurrence, according to a study published in the Journal of the American Medical Association.
Maarten C. Bosland, DVSc, PhD, from the University of Illinois at Chicago, and colleagues examined whether daily consumption of a soy protein isolate supplement for two years is associated with a reduction in the rate of biochemical recurrence of prostate cancer (PCa). Participants included 177 men at high risk of recurrence after RP who were randomized to receive a daily serving of a beverage powder containing 20 g of protein in the form of soy protein isolate (87 men) or calcium caseinate (placebo; 90 men).
Following lack of treatment effects at a planned interim analysis, the trial was stopped early. The researchers found that 28.3% of participants developed biochemical recurrence within two years of entering the trial. Within the intervention and placebo groups, recurrence was 27.2% and 29.5%, respectively. There were no supplementation-related adverse events recorded, and adherence was more than 90%.
“This randomized clinical trial demonstrated that development of biochemical recurrence of prostate cancer after radical prostatectomy was not reduced or delayed by daily consumption of a 20-g soy protein isolate supplement in men at high risk of recurrence, but the intervention appeared safe and was well tolerated,” the authors write.