Cancer Prevention Research, 06/27/2014 > Clinical Article
Albanes D, et al. – The authors examined whether pre–supplementation plasma α–tocopherol or γ–tocopherol was associated with overall or high–grade prostate cancer. The findings indicate that higher plasma α–tocopherol concentrations may interact with selenomethionine supplements to increase high–grade prostate cancer risk, suggesting a biological interaction between α–tocopherol and selenium itself or selenomethionine.
Abstract
The Selenium and Vitamin E Cancer Prevention Trial (SELECT) showed higher prostate cancer incidence in men supplemented with high-dose α-tocopherol. We therefore examined whether pre-supplementation plasma α-tocopherol or γ-tocopherol was associated with overall or high-grade prostate cancer. A stratified case-cohort sample that included 1,746 incident prostate cancer cases diagnosed through June, 2009 and a subcohort of 3,211 men was derived from the SELECT trial of 35,533 men. Plasma was collected at entry in 2001-2004, and median follow-up was 5.5 years (range, 0 – 7.9 years). Incidence of prostate cancer as a function of plasma α-tocopherol, γ-tocopherol, and supplementation with α-tocopherol or selenomethionine was estimated by the hazard ratio (HR). Plasma γ-tocopherol was not associated with prostate cancer. Men with higher α-tocopherol concentrations appeared to have risk similar to that of men with lower concentrations [overall HR for fifth (Q5) vs. first quintile (Q1), 1.21 (95% confidence interval (CI), 0.88-1.66, P-trend=0.24; in the trial placebo arm, Q5 HR, 0.85, 95% CI, 0.44-1.62, P-trend=0.66]. We found a strong positive plasma α-tocopherol association among men receiving the trial selenomethionine supplement [Q5 HR, 2.04, 95% CI, 1.29-3.22; P-trend=0.005]. A positive plasma α-tocopherol-prostate cancer association also appeared limited to high-grade disease (Gleason grade 7-10, overall Q5 HR, 1.59, 95% CI, 1.13-2.24, P-trend=0.001; among men receiving selenomethionine, HR, 2.12, 95% CI, 1.32-3.40; P-trend=0.0002). Our findings indicate that higher plasma α-tocopherol concentrations may interact with selenomethionine supplements to increase high-grade prostate cancer risk, suggesting a biological interaction between α-tocopherol and selenium itself or selenomethionine.