Safety of pregnancy after early breast cancer in young women with hormone receptor-positive disease: a systematic review and meta-analysis

Despite increasing evidence on the safety of pregnancy after anticancer treatments in breast cancer survivors, many physicians and patients continue to have concerns about a potential detrimental effect of pregnancy in patients with prior history of hormone receptor-positive breast cancer. A systematic literature search of Medline, Embase and Cochrane library with no language or date restriction up to January 1st, 2023, was performed. We included retrospective or prospective case-control and cohort studies as well as prospective clinical trials comparing survival outcomes of premenopausal female with reported pregnancy or not after diagnosis and treatment of hormone receptor-positive breast cancer. Included patients were childbearing potential age women with a prior history of hormone receptor-positive early breast cancer. Outcomes of interest were disease-free survival (DFS) and overall survival (OS). Hazard ratios (HR) with 95% confidence intervals (CI) were extracted. Eight studies were eligible to be included in the final analysis. A total of 3,805 patients with hormone receptor-positive breast cancer were included in this analysis, of whom 1,285 had a pregnancy after treatments. In the 3 studies (n=987 patients) reporting on DFS, no difference was observed between patients with or without a subsequent pregnancy (HR 0.96, 95% CI 0.75 – 1.24, p=0.781). Six studies (n=3,504 patients) reported OS: patients with a pregnancy after breast cancer had better OS than those without a pregnancy (HR 0.46, 95% CI 0.27 – 0.77, p<0.05). At the subgroup analysis on timing of pregnancy after breast cancer, no detrimental effect of pregnancy in terms of DFS was observed for patients achieving a late pregnancy (defined as 2 or 5 years after diagnosis) as compared to patients without a subsequent pregnancy (HR 1.08, 95% CI 0.80 – 1.46, p=0.611). Improved DFS was observed in patients with an early pregnancy (HR 0.63, 95% CI 0.47 – 0.85, p<0.05). Our results strengthen the evidence that having a pregnancy in women with prior history of hormone receptor-positive breast cancer is safe.