PHYSICAL ACTIVITY AND RISK OF BREAST CANCER

乳腺癌是最常见的癌症，也是美国女性癌症死亡的第二大原因。不幸的是，这种疾病的既定风险因素通常是不可改变的。 体育活动已被提出来降低乳腺癌的风险，几个合理的生物学机制确实支持这一假设。 然而，流行病学研究报告的结果高度不一致。由于病例对照研究比队列研究更一致地观察到反向关联，病例对照研究中的回忆偏差可能部分解释了这种差异。没有研究评估这种可能偏倚的程度。 此外，如果体力活动通过内源性激素机制影响乳腺癌风险，那么它应该与ER+/PR+乳腺癌更密切相关。 这个问题以前没有探讨过。 最后，目前还不清楚是否需要终身体育活动来降低乳腺癌风险;只有一项过去的研究对此进行了研究。 为了解决这些问题，我们建议在妇女健康研究（WHS）中使用已经收集的39，876名年龄大于或等于45岁的妇女的数据，以检查前瞻性确定的中年体力活动与所有乳腺癌（n=412）和仅ER+/PR+乳腺癌（n=222）风险的相关性。 此外，我们建议对这412名乳腺癌妇女和824名对照者进行病例对照研究，与随机分配到WHS的年龄和日期相匹配，现在将回顾性收集相同的体力活动信息。 这将允许评估任何可能的偏差，从病例对照研究有关的体力活动，乳腺癌的关系。此外，病例对照研究将收集12岁以来的身体活动信息，使我们能够评估终身身体活动。 这项建议，在相对较小的成本，将帮助我们更好地了解身体活动与乳腺癌的关系。

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer deaths among US women. Unfortunately, established risk factors for this disease generally are non-modifiable. Physical activity has been proposed to decrease breast cancer risk and several plausible biologic mechanisms do support this hypothesis. However, epidemiologic studies have reported highly inconsistent findings. Because case-control studies have more consistently observed inverse associations than have cohort studies, recall bias in case-control studies may account, partly, for the discrepancies. No study has assessed the extent of this possible bias. Further, if physical activity were to influence breast cancer risk via an endogenous hormonal mechanism, it should be more strongly related to breast cancers that are ER+/PR+. This question has not previously been explored. Finally, it is unclear whether lifetime physical activity is needed to decrease breast cancer risk; only one past study has examined this. To address these issues, we propose using already collected data from 39,876 women, aged greater than or equal to 45 years, in the Women's Health Study (WHS) to examine the associations of physical activity in middle-age, ascertained prospectively, with risk of all breast cancer (n=412) and of only ER+/PR+ breast cancers (n=222). Further, we propose to conduct a case-control study of these 412 women with breast cancer and 824 controls, matched to cases on age and date of randomization into the WHS, where the same information on physical activity now will be collected retrospectively. This will allow evaluation of any possible bias from case-control studies regarding the physical activity-breast cancer relation. Additionally, the case-control study will gather information on physical activity since age 12 years, allowing us to assess lifetime physical activity. This proposal, at relatively little cost, will help us better understand the physical activity-breast cancer relation.