RESUMO
BACKGROUND: The Selenium and Vitamin E Cancer Prevention Trial found no effect of selenium supplementation on prostate cancer (PCa) risk but a 17% increased risk from vitamin E supplementation. This case-cohort study investigates effects of selenium and vitamin E supplementation conditional upon baseline selenium status. METHODS: There were 1739 total and 489 high-grade (Gleason 7-10) PCa cases and 3117 men in the randomly selected cohort. Proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for effects of supplementation within quintiles of baseline toenail selenium. Cox proportional hazards models were used to estimate hazard ratios, and all statistical tests are two-sided. RESULTS: Toenail selenium, in the absence of supplementation, was not associated with PCa risk. Selenium supplementation (combined selenium only and selenium + vitamin E arms) had no effect among men with low selenium status (<60th percentile of toenail selenium) but increased the risk of high-grade PCa among men with higher selenium status by 91% (P = .007). Vitamin E supplementation (alone) had no effect among men with high selenium status (≥40th percentile of toenail selenium) but increased the risks of total, low-grade, and high-grade PCa among men with lower selenium status (63%, P = .02; 46%, P = .09; 111%, P = .008, respectively). CONCLUSIONS: Selenium supplementation did not benefit men with low selenium status but increased the risk of high-grade PCa among men with high selenium status. Vitamin E increased the risk of PCa among men with low selenium status. Men should avoid selenium or vitamin E supplementation at doses that exceed recommended dietary intakes.
Assuntos
Antioxidantes/efeitos adversos , Negro ou Afro-Americano/estatística & dados numéricos , Suplementos Nutricionais/efeitos adversos , Unhas/química , Neoplasias da Próstata/induzido quimicamente , Selênio/efeitos adversos , Vitamina E/efeitos adversos , Idoso , Antioxidantes/administração & dosagem , Antioxidantes/análise , Canadá/epidemiologia , Estudos de Coortes , Humanos , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Razão de Chances , Modelos de Riscos Proporcionais , Neoplasias da Próstata/epidemiologia , Neoplasias da Próstata/patologia , Porto Rico/epidemiologia , Ensaios Clínicos Controlados Aleatórios como Assunto , Risco , Selênio/administração & dosagem , Selênio/análise , Oligoelementos/efeitos adversos , Estados Unidos/epidemiologia , Vitamina E/administração & dosagem , Vitamina E/análise , Vitaminas/efeitos adversosRESUMO
Prostate cancer continues to be a major health threat, especially among African American men. The Selenium and Vitamin E Cancer Prevention Trial (SELECT), which opened on July 25, 2001, was planned to study possible agents for the prevention of prostate cancer in a population of 32,400 men in the United States, including Puerto Rico, and Canada. SELECT is a phase III randomized, placebo-controlled trial of selenium (200 microg/day from L-selenomethionine) and/or vitamin E (400 IU/day of all rac alpha-tocopheryl acetate) supplementation for a minimum of 7 years (maximum of 12 years) in non-African American men at least 55 years of age and African American men at least 50 years of age. SELECT is a large, simple trial that conforms as closely as possible with community standards of care. This commentary discusses the design problems the SELECT investigators had to resolve in developing the trial, including the role of prostate cancer screening, the best forms and doses of the study agents, and estimation of the event (prostate cancer) rate of men on the placebo arm.