J Clin Oncol

Breastfeeding after HR+ breast cancer is safe, feasible

September 2, 2025

Study details: The POSITIVE trial (NCT02308085) prospectively followed 313 women with early-stage hormone receptor-positive (HR+) breast cancer who paused endocrine therapy to pursue pregnancy. All participants had ≥1 live birth and were eligible for analysis of breastfeeding patterns and cancer outcomes. Median follow-up was 41 months.

Results: Of the cohort, 62.6% breastfed, most commonly for >4 months (median duration, 4.4 months). Breastfeeding was more frequent among women aged ≥35, those without prior children, and those who had breast-conserving surgery. The 24-month cumulative incidence of breast cancer events was similar between breastfeeding (3.6%) and non-breastfeeding (3.1%) groups (95% confidence interval, -4.3% to 5.2%).

Clinical impact: These findings offer reassurance that breastfeeding after HR+ breast cancer isn’t associated with increased short-term recurrence risk. The data support counseling patients that breastfeeding is both feasible and safe, even after breast-conserving surgery or unilateral mastectomy.

Source:

Peccatori FA, et al; International Breast Cancer Study Group and the POSITIVE Trial Collaborators. (2025, July 9). J Clin Oncol. Breastfeeding After Hormone Receptor-Positive Breast Cancer: Results From the POSITIVE Trial. https://pubmed.ncbi.nlm.nih.gov/40632989/