Phase 3 clinical trial investigating the effect of selenium supplementation in men at high‐risk for prostate cancer

Phase 3 randomized, double-blind, placebo-controlled, multi-center trial; 699 men under 80 years at high risk for prostate cancer (PSA >4 ng/mL and/or suspicious DRE and/or PSA velocity >0.75 ng/mL/year) with negative baseline biopsy; recruited from 20 sites in the United States and New Zealand; follow-up every six months for up to five years; three groups: placebo, selenium arm 1, selenium arm 2.

Placebo capsules daily; selenium in selenized yeast at 200 µg/day; selenium in selenized yeast at 400 µg/day; all taken orally once daily for up to five years.

Selenium supplementation did not reduce incidence of biopsy-proven prostate cancer compared with placebo. Hazard ratios for cancer incidence were 0.94 (95% CI 0.52–1.70) for 200 µg/day and 0.90 (95% CI 0.48–1.70) for 400 µg/day. PSA velocity did not differ significantly from placebo (p = 0.18 and p = 0.17). Conclusion: selenium at these doses does not reduce prostate cancer risk in high-risk men; unlikely to have a role in chemoprevention; results align with SELECT; potential explanations include baseline selenium status and selenium form differences across studies.

Trial stopped early for futility; changes in prostate biopsy technique during the study (increase in cores) may have affected cancer detection; dropout rates approximately 34–42% across groups; variation in baseline selenium status and use of high-selenium yeast formulation; multi-site international design.