Two international studies presented at the European Society for Medical Oncology (ESMO) Congress 2024 provide the first evidence that breastfeeding after breast cancer treatment does not increase the risk of recurrence or new breast cancers, even in women with germline BRCA mutations.

The first study, led by Eva Blondeaux, MD, of IRCCS Ospedale Policlinico San Martino in Genova, Italy, followed nearly 5,000 young women with germline BRCA mutations who had survived breast cancer. Of the 474 women who subsequently gave birth, 24% breastfed their babies. After a median follow-up of 7 years postpartum, there was no significant difference in breast cancer recurrences or new breast cancers between those who breastfed and those who did not (adjusted subdistribution hazard ratio, 1.08; 95% CI, 0.57-2.06; P = .82).

The second study, part of the international POSITIVE trial, included 518 women who temporarily interrupted their breast cancer treatment to have a baby. Of the 317 women who had at least 1 live birth, 62% breastfed. At 2 years postpartum, the proportion of women with breast cancer recurrence or new breast cancer was similar between those who breastfed (3.6%) and those who did not (3.1%).

These findings address previous concerns about the safety of breastfeeding after breast cancer, given the hormone-driven nature of many breast cancers and the hormonal changes associated with breastfeeding. Longer follow-up, however, may be needed to confirm the long-term safety of breastfeeding after breast cancer treatment.

"It's time to start thinking of breast cancer survivors as women with all the rights, needs, and possibilities of women that never had cancer," states Fedro Alessandro Peccatori, MD, Director of the Fertility & Procreation Unit at the European Institute of Oncology IRCCS in Milan, Italy, and a co-author of the POSITIVE study.

In addition to the BRCA-focused findings, the studies also extend beyond BRCA, with similar safety results observed in women with hormone receptor-positive early breast cancer. This additional data highlights the broad applicability of the findings to a larger group of breast cancer survivors.

While these results provide reassurance to breast cancer survivors who wish to breastfeed, longer follow-up may be needed to confirm the long-term safety of this practice.

Reference:

European Society for Medical Oncology. Studies provide first evidence that breastfeeding after breast cancer is safe. https://www.esmo.org/newsroom/press-and-media-hub/esmo-media-releases/studies-provide-first-evidence-that-breastfeeding-after-breast-cancer-is-safe