Breastfeeding after breast cancer in young BRCA carriers

Abstract

Breastfeeding; Breast cancer; BRCA carriers

Lactancia materna; Cáncer de mama; Portadoras de BRCA

Lactància materna; Càncer de mama; Portadores de BRCA

Background We investigated safety of breastfeeding after breast cancer in patients carrying germline BRCA pathogenic or likely pathogenic variants. Methods This was an international, multicenter, hospital-based, retrospective cohort study including BRCA carriers diagnosed with stage I–III invasive breast cancer at age 40 years or younger between January 2000 and December 2020 (NCT03673306). Locoregional recurrences and/or contralateral breast cancers, disease-free survival (DFS), and overall survival (OS) were compared between patients who breastfed after delivery and those who did not. Results Among 4732 patients included from 78 centers worldwide, 659 had a pregnancy after breast cancer diagnosis, of whom 474 delivered a child. After excluding patients with uptake of bilateral risk-reducing mastectomy prior to delivery (n = 225) or unknown breastfeeding status (n = 71), 110 (61.8%) breastfed (median duration 5 months) and 68 (38.2%) did not breastfeed. Compared to patients in the no breastfeeding group, those who breastfed were more frequently nulliparous at breast cancer diagnosis (61.8% vs 45.6%) and did not report prior smoking habit (71.8% vs 57.4%). After a median follow-up of 7.0 years following delivery, 7-year cumulative incidence of locoregional recurrences and/or contralateral breast cancers was 29% in the breastfeeding group and 36% in the no breastfeeding group (adjusted subdistribution hazard ratio [HR] = 1.08, 95% CI = 0.57 to 2.06). No difference in DFS (adjusted hazard ratio [aHR] = 0.83, 95% CI = 0.49 to 1.41) nor in OS (aHR = 1.32, 95% CI = 0.31 to 5.66) was observed. Conclusions Breastfeeding did not appear to be associated with a higher risk of developing locoregional recurrences or contralateral breast cancers, emphasizing the possibility of achieving a balance between maternal and infant needs without compromising oncological safety.

The study was partly supported by the Italian Association for Cancer Research (“Associazione Italiana per la Ricerca sul Cancro”, AIRC; MFAG 2020 ID 24698) and the 2022 Gilead Research Scholars Program in Solid Tumors with a focus on breast cancer. The funders of the study had no role in study design, data collection, analysis, interpretation, writing of the report, or decision to publish the manuscript and they had no access to the data. M.L. received support from the European Society for Medical Oncology (ESMO) for a translational research fellowship at the Institut Jules Bordet in Brussels, Belgium, at the time this study was initiated. H.J.K. receives support from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Republic of Korea (grant HC20C0135). A.H.P. receives support from the Breast Cancer Research Foundation and Susan G. Komen. K.A.P. is an Australian National Health and Medical Research Council leadership fellow. Data collection for most Australian participants was through the kConFab Follow-Up Study with support from Cancer Australia and the National Breast Cancer Foundation (PdCCRS 1100868), Cancer Australia (809195), the Australian National Breast Cancer Foundation (IF 17), the Australian National Health and Medical Research Council (454508, 288704, and 145684), the US National Institutes of Health (1RO1CA159868), the Queensland Cancer Fund, the Cancer Councils of New South Wales, Victoria, Tasmania, and South Australia, and the Cancer Foundation of Western Australia.