根据文章的背景资料：“在美国，男子在一生中罹患前列腺癌的风险目前估计为16%。尽管大多数的病例是在早期、可治愈的阶段被发现的，但该病治疗成本高，而且泌尿功能、性功能和与肠道相关的不良反应很常见。”有关硒和维生素E可降低前列腺癌风险的临床前及流行病学的证据是相当多的。 “在2008年12月发表的有关硒与维生素E癌症预防试验（SELECT）的最初的报告发现，无论是硒或是维生素E补充剂都不会降低前列腺癌的风险，而维生素E却会令前列腺癌的罹患风险出现非统计意义上的增加。较长的跟踪时间以及更多的前列腺癌事件令人们对维生素E与前列腺癌之间的关系有了进一步的了解。”
克里夫兰诊所的Eric A. Klein, M.D.及其同事对维生素E和硒对相对健康的男性的前列腺癌罹患风险的长期效应进行了调查。在select 中共有来自美国、加拿大和波多黎各的427个研究场所的3万5533名男子，他们是在2001年8月至2004年6月间进入这一随机化的试验中的。加入该研究的资格标准包括年龄在50岁或以上的黑人男子及年龄在55岁以上的其他种族男子，他们的前列腺特异性抗原（PSA）的测量低于某个浓度，直肠指检也没有怀疑他们罹患了前列腺癌。初步的分析包括了3万4887名男子，他们被随机分派到4个治疗组中的1组：8752人服用硒（200毫克/日）；8737人服用维生素E（400IU/日）；8702人服用硒和维生素E；8696人服用安慰剂；对这些受试者的计划跟踪时间最短为7年，最长为12年。分析反映的是由研究场所收集的他们的受试者的直到2011年7月5日时的最终数据。
自最初的报告以来，另外还有总共521人被诊断罹患了前列腺癌：113人来自安慰剂组，147人来自维生素E组，143人来自硒组，118人来自组合服药组。研究人员发现，在所有的治疗组中所发现的前列腺癌的发生率都高于安慰剂组，但只有维生素E组与安慰剂组的差异具有统计学上的显著性（即发现的前列腺癌发生率增加了17%）。与安慰剂组相比（该组有529人出现了前列腺癌），在维生素E组中有620人出现了前列腺癌，在硒组中有575人出现了前列腺癌，在硒加维生素E组中有555人出现了前列腺癌。在该试验的第三年，维生素E组与安慰剂组之间的前列腺癌发生率的差异变得明显。维生素E组中的低度和高度前列腺癌的预计风险都有所增加。
“所观察到的前列腺癌发生率增加了17%表明，看来无害但却有生物活性的物质（如维生素等）可能会引起损害。维生素E或其它制剂作为食物补充剂在预防常见的健康问题和癌症或提高总体存活率方面的裨益的缺乏，以及它们有可能造成伤害等都强调了在没有临床试验所证明的强有力的裨益证据时，消费者有必要对未加监督的非处方性柜台销售的产品所声称的对健康的益处持怀疑态度。”(生物谷 Bioon.com)
doi:10.1001/jama.2011.1437
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Vitamin E and the Risk of Prostate Cancer
Eric A. Klein, MD; Ian M. Thompson, Jr, MD; Catherine M. Tangen, DrPH; John J. Crowley, PhD; M. Scott Lucia, MD; Phyllis J. Goodman, MS; Lori M. Minasian, MD; Leslie G. Ford, MD; Howard L. Parnes, MD; J. Michael Gaziano, MD, MPH; Daniel D. Karp, MD; Michael M. Lieber, MD; Philip J. Walther, MD, PhD; Laurence Klotz, MD; J. Kellogg Parsons, MD, MHS; Joseph L. Chin, MD; Amy K. Darke, MS; Scott M. Lippman, MD; Gary E. Goodman, MD; Frank L. Meyskens, Jr, MD; Laurence H. Baker, DO
Context The initial report of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) found no reduction in risk of prostate cancer with either selenium or vitamin E supplements but a statistically nonsignificant increase in prostate cancer risk with vitamin E. Longer follow-up and more prostate cancer events provide further insight into the relationship of vitamin E and prostate cancer.
Objective To determine the long-term effect of vitamin E and selenium on risk of prostate cancer in relatively healthy men.
Design, Setting, and Participants A total of 35 533 men from 427 study sites in the United States, Canada, and Puerto Rico were randomized between August 22, 2001, and June 24, 2004. Eligibility criteria included a prostate-specific antigen (PSA) of 4.0 ng/mL or less, a digital rectal examination not suspicious for prostate cancer, and age 50 years or older for black men and 55 years or older for all others. The primary analysis included 34 887 men who were randomly assigned to 1 of 4 treatment groups: 8752 to receive selenium; 8737, vitamin E; 8702, both agents, and 8696, placebo. Analysis reflect the final data collected by the study sites on their participants through July 5, 2011.
Interventions Oral selenium (200 μg/d from L-selenomethionine) with matched vitamin E placebo, vitamin E (400 IU/d of all rac-α-tocopheryl acetate) with matched selenium placebo, both agents, or both matched placebos for a planned follow-up of a minimum of 7 and maximum of 12 years.
Main Outcome Measures Prostate cancer incidence.
Results This report includes 54 464 additional person-years of follow-up and 521 additional cases of prostate cancer since the primary report. Compared with the placebo (referent group) in which 529 men developed prostate cancer, 620 men in the vitamin E group developed prostate cancer (hazard ratio [HR], 1.17; 99% CI, 1.004-1.36, P = .008); as did 575 in the selenium group (HR, 1.09; 99% CI, 0.93-1.27; P = .18), and 555 in the selenium plus vitamin E group (HR, 1.05; 99% CI, 0.89-1.22, P = .46). Compared with placebo, the absolute increase in risk of prostate cancer per 1000 person-years was 1.6 for vitamin E, 0.8 for selenium, and 0.4 for the combination.
Conclusion Dietary supplementation with vitamin E significantly increased the risk of prostate cancer among healthy men.
