Daling J R, Malone K E, Voigt L F, White E, Weiss N S
Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
J Natl Cancer Inst. 1994 Nov 2;86(21):1584-92. doi: 10.1093/jnci/86.21.1584.
Certain events of reproductive life, especially completed pregnancies, have been found to influence a woman's risk of breast cancer. Prior studies of the relationship between breast cancer and a history of incomplete pregnancies have provided inconsistent results. Most of these studies included women beyond the early part of their reproductive years at the time induced abortion became legal in the United States.
We conducted a case-control study of breast cancer in young women born recently enough so that some or most of their reproductive years were after the legalization of induced abortion to determine if certain aspects of a woman's experience with abortion might be associated with risk of breast cancer.
Female residents of three counties in western Washington State, who were diagnosed with breast cancer (n = 845) from January 1983 through April 1990, and who were born after 1944, were interviewed in detail about their reproductive histories, including the occurrence of induced abortion. Case patients were obtained through our population-based tumor registry (part of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute). Similar information was obtained from 961 control women identified through random digit dialing within these same counties. Logistic regression analysis was used to estimate odds ratios and confidence intervals (CIs).
Among women who had been pregnant at least once, the risk of breast cancer in those who had experienced an induced abortion was 50% higher than among other women (95% CI = 1.2-1.9). While this increased risk did not vary by the number of induced abortions or by the history of a completed pregnancy, it did vary according to the age at which the abortion occurred and the duration of that pregnancy. Highest risks were observed when the abortion was done at ages younger than 18 years--particularly if it took place after 8 weeks' gestation--or at 30 years of age or older. No increased risk of breast cancer was associated with a spontaneous abortion (RR = 0.9; 95% CI = 0.7-1.2).
Our data support the hypothesis that an induced abortion can adversely influence a woman's subsequent risk of breast cancer. However, the results across all epidemiologic studies of this premise are inconsistent--both overall and within specific subgroups. The risk of breast cancer should be reexamined in future studies of women who have had legal abortion available to them throughout the majority of their reproductive years, with particular attention to the potential influence of induced abortion early in life.
已发现生殖生活中的某些事件，尤其是足月妊娠，会影响女性患乳腺癌的风险。先前关于乳腺癌与不完全妊娠史之间关系的研究结果并不一致。这些研究大多纳入了在美国人工流产合法化时已过生育早期的女性。
我们对近期出生的年轻女性进行了一项乳腺癌病例对照研究，这些女性的部分或大部分生育年份是在人工流产合法化之后，以确定女性人工流产经历的某些方面是否可能与乳腺癌风险相关。
对1983年1月至1990年4月期间在华盛顿州西部三个县被诊断为乳腺癌（n = 845）且出生于1944年以后的女性居民，详细询问其生殖史，包括人工流产情况。病例患者通过我们基于人群的肿瘤登记处（美国国立癌症研究所监测、流行病学和最终结果计划的一部分）获得。从这些县内通过随机数字拨号确定的961名对照女性中获取类似信息。采用逻辑回归分析来估计比值比和置信区间（CI）。
在至少怀孕过一次的女性中，经历过人工流产的女性患乳腺癌的风险比其他女性高50%（95%CI = 1.2 - 1.9）。虽然这种增加的风险并不因人工流产次数或足月妊娠史而有所不同，但确实因人工流产时的年龄和妊娠持续时间而有所不同。当人工流产在18岁以下进行时，尤其是在妊娠8周后进行，或在30岁及以上进行时，观察到的风险最高。自然流产与乳腺癌风险增加无关（RR = 0.9；95%CI = 0.7 - 1.2）。
我们的数据支持人工流产会对女性随后患乳腺癌的风险产生不利影响这一假设。然而，关于这一前提的所有流行病学研究结果在总体上以及在特定亚组内都是不一致的。在未来对在其大部分生育年份都可进行合法人工流产的女性的研究中，应重新审视乳腺癌风险，尤其要关注早年人工流产的潜在影响。
