Oral Selenium Supplementation Has No Effect on Prostate-Specific Antigen Velocity in Men Undergoing Active Surveillance for Localized Prostate Cancer

Randomized, placebo-controlled multicenter trial in men with biopsy-proven localized, nonmetastatic prostate cancer who chose active surveillance rather than immediate treatment. For the 200 μg/day selenium group, 47 participants were randomized; for the 800 μg/day selenium group, 47 participants were randomized. Participants were older men, predominantly Caucasian, with localized disease and baseline PSA and selenium levels reported at entry.

Men on active surveillance received oral selenized yeast at either 200 μg/day or 800 μg/day, taken daily for up to 5 years, compared with placebo. The active intervention was selenium supplementation alone; no other study supplement was part of the tested regimen.

Selenium did not slow prostate cancer progression as measured by PSA velocity. Compared with placebo, PSA velocity differences were not significant for 200 μg/day (-0.03, 95% CI -0.09 to 0.03; P = 0.32) or 800 μg/day (-0.02, 95% CI -0.08 to 0.04; P = 0.61). In quartile analyses, the 800 μg/day group showed a higher PSA velocity than placebo in the highest baseline selenium quartile (P = 0.018), while lower quartiles were not significantly different. Time to treatment was also not significantly different by Kaplan-Meier estimates, supporting the conclusion that selenium supplementation did not prevent progression of localized prostate cancer and may have been harmful in men with high baseline selenium.

The active intervention arms were small, with 47 participants randomized per dose, limiting power for subgroup and adverse event analyses. Follow-up and interpretation were complicated by heterogeneity in baseline selenium status, and the signal of harm was limited to a post hoc high-selenium subgroup. Generalizability is also limited to older, mostly Caucasian men with localized prostate cancer on active surveillance.