Newcomb P A, Egan K M, Titus-Ernstoff L, Trentham-Dietz A, Greenberg E R, Baron J A, Willett W C, Stampfer M J
Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
Am J Epidemiol. 1999 Jul 15;150(2):174-82. doi: 10.1093/oxfordjournals.aje.a009977.
A modest inverse association between lactation and breast cancer risk has most consistently been observed in premenopausal women, and certain breastfeeding patterns, such as prolonged duration and early age at first lactation, may be important determinants of risk. However, these associations have not generally been observed in relation to postmenopausal breast cancer. As part of a multicenter population-based case-control study, the authors examined postmenopausal breast cancer risk according to breastfeeding characteristics. Breast cancer patients aged 50-79 years were identified from statewide tumor registries in Massachusetts, New Hampshire, and Wisconsin from July 1992 through July 1995. Similarly aged control women were randomly selected from population lists. Information regarding lactation history and breast cancer risk factors was obtained through telephone interviews. This analysis included only data on parous postmenopausal women (3,633 cases and 3,790 controls). After adjustment for age, parity, age at first birth, and other breast cancer risk factors, breastfeeding for at least 2 weeks was associated with a slightly reduced risk of breast cancer in comparison with women who had never lactated (relative risk = 0.87, 95% confidence interval 0.78-0.96). There was only a modest suggestion that increasing cumulative duration of lactation was inversely associated with breast cancer risk; the relative risk for women who had breastfed for > or =24 months was 0.73 (95% confidence interval 0.56-0.94) (p-trend for duration = 0.10). Age at first lactation was not consistently associated with risk. Modest inverse associations appeared to persist even up to 50 years since first lactation. Use of hormones to suppress lactation was not associated with postmenopausal breast cancer, nor was inability to breastfeed related to risk. These results suggest that lactation may have a slight and perhaps long-lasting protective effect on postmenopausal breast cancer risk.
哺乳期与乳腺癌风险之间适度的负相关关系在绝经前女性中最为一致地被观察到，并且某些母乳喂养模式，如持续时间延长和首次哺乳年龄较早，可能是风险的重要决定因素。然而，这些关联在绝经后乳腺癌方面通常未被观察到。作为一项基于人群的多中心病例对照研究的一部分，作者根据母乳喂养特征研究了绝经后乳腺癌风险。1992年7月至1995年7月期间，从马萨诸塞州、新罕布什尔州和威斯康星州的全州肿瘤登记处确定了年龄在50 - 79岁的乳腺癌患者。同样年龄的对照女性从人口名单中随机选取。通过电话访谈获取了有关哺乳史和乳腺癌风险因素的信息。该分析仅包括经产绝经后女性的数据（3633例病例和3790例对照）。在对年龄、产次、首次生育年龄和其他乳腺癌风险因素进行调整后，与从未哺乳的女性相比，哺乳至少2周与乳腺癌风险略有降低相关（相对风险 = 0.87，95%置信区间0.78 - 0.96）。仅有适度的迹象表明，哺乳累积持续时间增加与乳腺癌风险呈负相关；哺乳≥24个月的女性的相对风险为0.73（95%置信区间0.56 - 0.94）（持续时间的p趋势 = 0.10）。首次哺乳年龄与风险之间没有始终如一的关联。即使在首次哺乳后长达50年，适度的负相关关系似乎仍然存在。使用激素抑制泌乳与绝经后乳腺癌无关，无法母乳喂养也与风险无关。这些结果表明，哺乳可能对绝经后乳腺癌风险有轻微且可能持久的保护作用。
