Safety of pregnancy in women with history of estrogen receptor (ER)–positive breast cancer remains controversial. In this multicenter case–control study, 333 patients with pregnancy after breast cancer were matched (1:3) to 874 nonpregnant patients of similar characteristics, adjusting for guaranteed time bias. Survival estimates were calculated using the Kaplan-Meier analysis; groups were compared with the log-rank test. All reported P values were two-sided. At a median follow-up of 7.2 years after pregnancy, no difference in disease-free survival was observed between pregnant and nonpregnant patients with ER-positive (hazard ratio [HR] = 0.94, 95% confidence interval [CI] = 0.70 to 1.26, P = .68) or ER-negative (HR = 0.75, 95% CI = 0.53 to 1.06, P = .10) disease. No overall survival (OS) difference was observed in ER-positive patients (HR = 0.84, 95% CI = 0.60 to 1.18, P = .32); ER-negative patients in the pregnant cohort had better OS (HR = 0.57, 95% CI = 0.36 to 0.90, P = .01). Abortion, time to pregnancy, breastfeeding, and type of adjuvant therapy had no impact on patients’ outcomes. This study provides reassuring evidence on the long-term safety of pregnancy in breast cancer survivors, including those with ER-positive disease.

中文翻译：

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根据雌激素受体状态确定乳腺癌后妊娠的长期安全性

有雌激素受体（ER）阳性乳腺癌病史的女性怀孕的安全性仍然存在争议。在这项多中心病例对照研究中，将 333 名乳腺癌后妊娠患者与 874 名具有相似特征的非妊娠患者进行匹配 (1:3)，并调整了保证时间偏差。使用 Kaplan-Meier 分析计算生存估计值；组间比较采用对数秩检验。所有报告的P值都是双向的。在怀孕后 7.2 年的中位随访中，ER 阳性的怀孕和非怀孕患者之间没有观察到无病生存率的差异（风险比 [HR] = 0.94，95% 置信区间 [CI] = 0.70 至 1.26） ，P = .68）或 ER 阴性（HR = 0.75，95% CI = 0.53 至 1.06，P = .10）疾病。ER 阳性患者中未观察到总生存期 (OS) 差异（HR = 0.84，95% CI = 0.60 至 1.18，P = .32）；妊娠队列中 ER 阴性患者的 OS 较好（HR = 0.57，95% CI = 0.36 至 0.90，P = 0.01）。流产、怀孕时间、母乳喂养和辅助治疗类型对患者的结果没有影响。这项研究为乳腺癌幸存者（包括 ER 阳性患者）怀孕的长期安全性提供了令人放心的证据。