Saw Palmetto Use and Risk of Prostate Cancer

描述(由申请人提供)： 除了非黑色素瘤皮肤癌，前列腺癌是当今美国男性中最常见的被诊断为癌症的癌症。尽管它很重要，但几乎没有建立起这种疾病的可修改的预测因子。已确定的前列腺癌危险因素(如年龄)不能修改，因此，作为一级预防策略的目标的效用有限。有必要确定其他可以控制的风险因素。5-α还原酶是一种将睾酮转化为二氢睾酮的酶，已被提出在前列腺癌的病因中发挥关键作用；因此，NCI目前正在进行一项随机临床试验，测试5-α还原酶抑制剂非那雄胺在预防前列腺癌中的作用。目前还没有关于其他能够抑制5-α还原酶和男性前列腺癌风险的药物的信息。 从美国棕榈树的浆果中提取的锯棕榈树可以抑制5-α还原酶的活性。锯棕榈已被证明在治疗良性前列腺增生症的尿路症状方面与非那雄胺一样有效。目前还没有关于它与男性前列腺癌发病率之间关系的数据；然而，体外研究表明，它抑制了前列腺癌细胞系的生长。因此，我们建议对16,700名医生(平均年龄67岁)进行一项回溯性队列研究，以检验使用棕榈油可降低患前列腺癌风险的假设。这两名男性目前正作为另外两项资助研究的一部分--医生健康研究I和II--进行跟踪。这两项研究收集了前列腺癌的发病信息，以及有关健康习惯和病史的大量其他信息。 在这项申请中，我们建议通过在另外两项研究中预定的72个月随访问卷中添加问题来回顾收集有关锯棕榈使用的细节(何时开始和停止、剂量、品牌)。在拟议的研究期间，我们预计将发生790例前列腺癌。功率计算表明，足够的功率可以检测到与使用锯棕榈相关的前列腺癌风险降低45%。在几乎没有额外成本的情况下，这项研究的数据将有助于知识基础设施，关于锯棕榈使用和前列腺癌风险的大规模、信息丰富的试验是否应该在未来得到支持。

DESCRIPTION (provided by applicant): Apart from non-melanoma skin cancer, prostate cancer is the most commonly diagnosed cancer among men in the United States today. In spite of its importance, few modifiable predictors of this disease have been established. Well-established risk factors for prostate cancer (e.g., age) are not amenable to modification and, hence, have limited utility as targets of primary prevention strategies. There is a need to identify other risk factors that can be controlled. 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone, has been proposed to play a key role in the etiology of prostate cancer; thus, the NCI is currently testing finasteride, a 5-alpha reductase inhibitor, in the prevention of prostate cancer in an ongoing, randomized clinical trial. No information is available on other agents capable of inhibiting 5-alpha reductase and prostate cancer risk in men. Saw palmetto, derived from the berry of the American palm tree, can inhibit 5-alpha reductase activity. Saw palmetto has been shown to be as effective as finasteride in the treatment of urinary symptoms from benign prostatic hyperplasia. No data are available regarding its association with prostate cancer incidence in men; however, in vitro studies show inhibition of growth of prostate cancer cell lines. Therefore, we propose to conduct a retrospective cohort study among 16,700 physicians (mean age 67 years) to test the hypothesis that saw palmetto use reduces the risk of developing prostate cancer. These men currently are being followed as part of two other funded studies, the Physicians' Health Study I and II. Information on the development of prostate cancer is being collected in these two studies, as is a whole host of other information on health habits and medical history. In this application, we propose to retrospectively collect details on the use of saw palmetto (when started and stopped, dose, brand) by adding questions to the scheduled 72-month follow-up questionnaire in these two other studies. During the proposed period of study, we anticipate that 790 cases of prostate cancer will develop. Power calculations show adequate power to detect a 45% reduction in risk of prostate cancer associated with saw palmetto use. At little additional cost, the data from this study will contribute to the knowledge infrastructure regarding whether large scale, informative trials on saw palmetto use and prostate cancer risk should be supported in the future.