Bardia Aditya, Hartmann Lynn C, Vachon Celine M, Vierkant Robert A, Wang Alice H, Olson Janet E, Sellers Thomas A, Cerhan James R
Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Arch Intern Med. 2006;166(22):2478-83. doi: 10.1001/archinte.166.22.2478.
Physical activity is a potentially modifiable breast cancer risk factor. There is considerable recent evidence to suggest that risk factors for breast cancer differ based on its subtype, particularly estrogen receptor (ER)/progesterone receptor (PR) status, but this has been less well studied for physical activity. The objective of this study was to examine the association of physical activity with breast cancer incidence based on ER/PR status of the tumor.
The Iowa Women's Health Study is a prospective cohort study of 41 836 postmenopausal women. Recreational physical activity was self-reported on the baseline questionnaire, and 3 levels (high, medium, and low) were defined. Breast cancer incidence and ER/PR status, through 18 years of follow-up, were ascertained by linkage with the Iowa Surveillance, Epidemiology, and End Results Cancer Registry. Cox proportional hazards models were used to estimate multivariate relative risks (RRs) and 95% confidence intervals (CIs) of breast cancer, adjusting for other breast cancer risk factors.
During 554 819 person-years of follow-up, 2548 incident cases of breast cancer were observed. Compared with low physical activity, high physical activity levels were inversely associated with risk of breast cancer (RR, 0.86; 95% CI, 0.78-0.96), and there were inverse associations for ER-positive (ER+)/PR-positive (RR, 0.87; 95% CI, 0.75-1.00), ER+/PR-negative (PR-) (RR, 0.67; 95% CI, 0.47-0.96), and ER-negative/PR- (RR, 0.80; 95% CI, 0.56-1.14) tumors. Further adjustment for body mass index attenuated the overall association with breast cancer (RR, 0.91; 95% CI, 0.82-1.01) and for ER+/PR-positive tumors (RR, 0.94; 95% CI, 0.81-1.08), while there was no change for ER+/PR- tumors (RR, 0.66; 95% CI, 0.46-0.94).
Higher recreational physical activity might reduce the risk of postmenopausal breast cancer overall. Risk reduction varies by ER/PR status of the tumor, being most marked for ER+/PR- tumors, which, in general, have been associated with a clinically more aggressive tumor phenotype. If confirmed in additional studies, these results would suggest that additional mechanisms, besides an effect on body mass, may account for observed protective effects of physical activity in reducing breast cancer.
身体活动是一个潜在的可改变的乳腺癌风险因素。最近有大量证据表明，乳腺癌的风险因素因其亚型不同而有所差异，尤其是雌激素受体（ER）/孕激素受体（PR）状态，但身体活动在这方面的研究较少。本研究的目的是根据肿瘤的ER/PR状态，研究身体活动与乳腺癌发病率之间的关联。
爱荷华州妇女健康研究是一项对41836名绝经后妇女进行的前瞻性队列研究。通过基线调查问卷自我报告休闲身体活动情况，并定义了三个水平（高、中、低）。通过与爱荷华州监测、流行病学和最终结果癌症登记处的数据链接，确定了18年随访期间的乳腺癌发病率和ER/PR状态。使用Cox比例风险模型估计乳腺癌的多变量相对风险（RR）和95%置信区间（CI），并对其他乳腺癌风险因素进行调整。
在554819人年的随访期间，观察到2548例乳腺癌发病病例。与低身体活动水平相比，高身体活动水平与乳腺癌风险呈负相关（RR，0.86；95%CI，0.78 - 0.96），对于ER阳性（ER+）/PR阳性（RR，0.87；95%CI，0.75 - 1.00）、ER+/PR阴性（PR-）（RR，0.67；95%CI，0.47 - 0.96）和ER阴性/PR-（RR，0.80；95%CI，0.56 - 1.14）肿瘤也存在负相关。进一步调整体重指数后，总体上与乳腺癌的关联减弱（RR，0.91；95%CI，0.82 - 1.01），与ER+/PR阳性肿瘤的关联也减弱（RR，0.94；95%CI，0.81 - 1.08），而ER+/PR-肿瘤的关联无变化（RR，0.66；95%CI，0.46 - 0.94）。
较高的休闲身体活动可能总体上降低绝经后乳腺癌的风险。风险降低因肿瘤的ER/PR状态而异，对于ER+/PR-肿瘤最为明显（这类肿瘤通常与临床上更具侵袭性的肿瘤表型相关）。如果在其他研究中得到证实，这些结果将表明，除了对体重的影响外，可能还有其他机制可以解释身体活动在降低乳腺癌风险方面所观察到的保护作用。
