Breastfeeding does not increase the risk of breast cancer recurrence

Breastfeeding is feasible among young breast cancer survivors, including BRCA carriers, and is mostly performed in the contralateral breast. Breastfeeding does not increase the risk of breast cancer recurrence. These were the main findings of the POSITIVE trial and the BRCA BCY cohort study.

Young breast cancer survivors face significant challenges, including fertility issues. Recently, the prospective, single-arm POSITIVE trial (NCT02308085) showed that for women with HR+ breast cancer, temporary interruption of adjuvant endocrine therapy to attempt pregnancy is safe and does not confer a greater short-term risk of breast cancer events [1].

Dr Fedro Peccatori (European Institute of Oncology, Italy) presented results on breastfeeding feasibility and safety outcomes, a secondary endpoint of the POSITIVE study [2]. The trial enrolled 518 participants (aged between 18 and 42 years) with HR+ stage I–III breast cancer wishing to become pregnant. Participants stopped endocrine therapy for up to 2 years to allow conception, delivery, and (optional) breastfeeding.

Of 313 participants who did not have a bilateral mastectomy, 196 (62%) started breastfeeding after delivery (83.6% nullipara). Most mothers breastfed from the contralateral breast only (69.2%), 29.2% breastfed from both breasts, and 1.5% breastfed from the affected breast only. Factors associated with a higher frequency of breastfeeding were breast-conserving therapy, age >35 years, nulliparity, and enrolment in Asia, the Pacific, or the Middle East. Breastfeeding was not associated with any new breast cancer events up to 41 months of follow-up (event rates of 3.6% in women who breastfed vs 3.1% in women who did not breastfeed).

Similar results were obtained in an international retrospective cohort study (BRCA BCY Collaboration [NCT03673306]), presented by Dr Eva Blondeaux (University of Genova, Italy) [3,4]. No increased risk for breast cancer events (locoregional or contralateral recurrence) was observed in BRCA carriers who breastfed after delivery (n=110) versus BRCA carriers who did not breastfeed (n=68). The 7-year cumulative incidence of breast cancer events was 29% in the breastfeeding group and 37% in the non-breastfeeding group (HR 1.08; 95% CI 0.57–2.06; P=0.818). In addition, no difference was observed in both disease-free and overall survival.

In conclusion, breastfeeding is feasible for young breast cancer survivors, including BRCA carriers, and does not increase the risk of breast cancer recurrence.

1. Partridge AH, et al. N Engl J Med 2023;388:1645-1656.
2. Azim HA, et al. Breastfeeding in women with hormone receptor-positive breast cancer who conceived after temporary interruption of endocrine therapy: Results from the POSITIVE trial. Abstract 1814O, ESMO Congress 2024, 13–17 September, Barcelona, Spain.
3. Lambertini M et al. JAMA. 2024;331:49-59.
4. Blondeau E, et al. Breastfeeding after breast cancer in young BRCA carriers: Results from an international cohort study. Abstract 1815O, ESMO Congress 2024, 13–17 September, Barcelona, Spain.

 

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Posted on 4 November 2024