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癌症。尽管它的重要性，很少有可修改的预测这种疾病已经建立。明确的前列腺癌风险因素（例如，年龄）不能修改，因此作为初级预防战略的目标的效用有限。有必要确定可以控制的其他风险因素。5-α-还原酶是一种将睾酮转化为二氢睾酮的酶，已被认为在前列腺癌的病因学中起关键作用;因此，NCI目前正在进行一项正在进行的随机临床试验中测试5-α还原酶抑制剂finaldide预防前列腺癌。没有关于能够抑制5-α还原酶和男性前列腺癌风险的其他药物的信息。 锯棕榈，来自美国棕榈树的浆果，可以抑制5-α还原酶活性。锯棕榈已被证明是一样有效的治疗良性前列腺增生症的泌尿系统症状。没有关于其与男性前列腺癌发病率相关的数据;然而，体外研究显示其抑制前列腺癌细胞系的生长。因此，我们建议在16,700名医生（平均年龄67岁）中进行一项回顾性队列研究，以检验使用锯棕榈降低患前列腺癌风险的假设。这些人目前正在跟踪的一部分，其他两个资助的研究，医生的健康研究I和II。这两项研究收集了有关前列腺癌发展的信息，以及有关健康习惯和病史的大量其他信息。 在本申请中，我们建议通过在这两项其他研究的计划72个月随访问卷中添加问题，回顾性收集有关使用锯棕榈的详细信息（开始和停止时间、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。功效计算显示，有足够的功效检测与使用锯棕榈相关的前列腺癌风险降低45%。在很少的额外费用，从这项研究的数据将有助于知识的基础设施，是否大规模，信息试验锯棕榈的使用和前列腺癌的风险，应支持在未来。

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.