SWOG S0000: SELENIUM AND VITAMIN E CANCER PREVENTION TRIAL (SELECT)

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。在过去十年中，前列腺癌一直是美国男性中最常见的恶性肿瘤（不包括非黑色素瘤皮肤癌）。据估计，白种人男性患前列腺癌的终生风险为16.6%，非裔美国男性为18.1%，50岁男性患前列腺癌的总死亡风险为2.9% （Ries等，1998年，Scher等，1995年）。降低前列腺癌死亡率和发病率的理想方法是通过一级预防：要么减少危及生命的临床明显病例的数量，要么降低该疾病的年龄依赖性发展速度，即，该疾病将比其他情况晚5年、10年、15年变得明显。虽然有证据表明这种肿瘤的发展可能与饮食习惯有关，但改变这种行为模式的问题以及终身干预的必要性使得这种预防方法在实践中很难（Mishina等人，1985）。本研究的目的是比较研究补充剂的效果。这些补充剂是硒（l -硒代蛋氨酸）、维生素E （α -生育酚）、硒加维生素E和安慰剂（不含活性物质的药丸）。我们想看看除了安慰剂之外，这些补充剂是否能预防或减少前列腺癌的发生。硒和维生素E在预防前列腺癌方面的潜在作用最有力的证据来自两项随机、安慰剂对照的临床试验的次要发现。这两种补充剂的发展已经到了需要随机、安慰剂对照干预的阶段，以检验关于这两种补充剂的前列腺癌化学预防作用的主要假设（Taylor, Albanes, 1998）。数据表明，硒和维生素E的活性是互补的，这两种补充剂协同作用，抑制致癌作用（Hoekstra, 1975; Medina, 1986; Thompson, 1994）。这一证据使得同时测试两种补充剂的2x2析因设计成为验证性III期试验的特别有吸引力的选择。目前还没有研究同时使用硒和维生素E的效果。根据过去使用其他药物以及我们在这里测试的两种补充剂的研究，我们相信男性可能会从同时使用这两种补充剂中获得额外的好处。这项试验的主要目的是了解在常规医疗保健中发现的健康男性前列腺癌的更多信息。我们想知道研究补充剂是否能预防或减少这些癌症。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Prostate cancer has been the most common malignant tumor (excluding non-melanoma skin cancer) in U.S. men for the last decade. It has been estimated that the lifetime risk of developing prostate cancer is 16.6% for Caucasian males and 18.1% for African-American males, and the overall prostate cancer mortality risk for men age 50 is 2.9% (Ries, et. al. 1998, Scher; et. al. 1995). An ideal method to reduce the mortality and morbidity of carcinoma of the prostate would be through primary prevention: either through a reduction in the number of life-threatening, clinically-evident cases or through a reduced age-dependent rate of development of the disease, i.e., the disease would become evident 5, 10, 15 years later than otherwise would occur. Although there is evidence that the development of this tumor may be related to dietary habits, problems in changing such patterns of behavior and the need for life-long intervention make such a preventative method difficult in practice (Mishina, et. al., 1985). The purpose of this study is to compare the effects of the study supplements. The supplements are selenium (L-selenomethionine), vitamin E (alpha-tocopherol), selenium plus vitamin E and placebo (a pill containing no active substances). We want to see whether the supplements, other than the placebo, can prevent or reduce the occurrance of prostate cancer. In both selenium and vitamin E, the strongest evidence for their potential roles in preventing prostate cancer comes from secondary findings of two randomized, placebo-controlled clinical trials. The development of these two supplements has arrived at the stage where a randomized, placebo-controlled intervention is needed to test the primary hypothesis regarding these supplements' prostate cancer chemoprevention effects (Taylor, Albanes, 1998). Data indicate that activities of selenium and vitamin E are complementary and that the two supplements act synergistically to inhibit carcinogenesis (Hoekstra, 1975; Medina, 1986; Thompson, 1994). This evidence makes the 2x2 factorial design for simultaneously testing both supplements a particularly attractive option for the confirmatory Phase III trial. No studies looking at the effect of using both selenium and vitamin E have been done. Based on past studies using other agents as well as the two supplements we are testing here, we believe that men may get an added benefit from using these two supplements together. The main purpose of this trial is to learn more about prostate cancers in healthy men that are found as part of regular medical care. We want to know whether the study supplements can prevent or decrease these cancers.