According to the results of a study published early online in the Journal of Clinical Oncology, a combination of vitamin E, selenium, and soy protein does not prevent the progression of high-grade prostatic intraepithelial neoplasia (HGPIN) to invasive prostate cancer (PCa).

The Phase III study randomised 303 men with confirmed HGPIN to double-blind treatment with a nutritional supplement containing daily soy (20 g), vitamin E (400 U), and selenium (100 μg) or a whey-based placebo twice daily for three years. The primary endpoint was disease-free survival (DFS; defined as the time to diagnosis of PCa); Kaplan-Meier plots and log-rank tests were used to compare the two treatment groups.

The authors report that the nutritional supplement had no impact on the development of invasive PCa – the annual incidence was 0.16 (95% CI 0.11 to 0.20) for participants in the nutritional supplement arm and 0.15 (95% CI 0.10 to 0.19) for those in the placebo arm.  The 2-year DFS rates were 68.9% and 73.4%, respectively (hazard ratio 1.03; 95% CI 0.67 to 1.61).

The authors conclude that ‘based on the accumulated data surrounding the preventative properties of vitamin E, selenium, and soy product, it can be concluded that these agents have no role in the primary prevention of invasive PCa in men with HGPIN at biopsy’.