Breastfeeding Safely Is Possible Following Breast Cancer

BARCELONA, Spain — Breastfeeding is possible even after breast cancer, according to findings from two international studies led by Italian researchers, presented at the European Society for Medical Oncology (ESMO) Annual Meeting 2024.

“Before this data, doctors tended to be cautious, if not outright defensive, about the possibility and safety of breastfeeding [following breast cancer],” said Fedro Alessandro Peccatori, MD, PhD, director of the Procreation and Fertility Unit at the European Institute of Oncology in Milan, Italy, and lead author of a study that reported results from the POSITIVE trial. He was speaking with Univadis Italy, a Medscape Network platform.

Doctors have been concerned about potential risks for breastfeeding following breast cancer due to the altered hormonal status that occurs during pregnancy and lactation because many breast cancers are hormone responsive.

“These considerations also apply to women carrying a BRCA gene mutation who have an increased risk of cancer in the contralateral breast,” said Eva Blondeaux, MD, an oncologist at IRCCS Ospedale Policlinico San Martino in Genoa, Italy, who discussed the results of the second study involving women who have the mutation with Univadis Italy.

Reassuring Data for Young Women

The two studies, despite their differences, showed that breast cancer should not preclude the possibility of breastfeeding.

The POSITIVE study involved 518 women (from 116 institutions in 20 countries across four continents) with hormone receptor–positive breast cancer who had temporarily stopped adjuvant hormonal treatment to become pregnant.

In total, 317 women successfully completed at least one pregnancy and 62% breastfed. The analyses revealed no significant differences in the rates of recurrence at 24 months or new breast cancer between women who breastfed and those who did not (3.6% vs 3.1%).

The second study involved 4732 women recruited from 78 international centers who were diagnosed with breast cancer at a young age and were carriers of a BRCA gene mutation. Of the 474 women who gave birth, 110 (23.2%) breastfed.

Importantly, about half of the women involved in the study underwent preventive bilateral mastectomy before giving birth. This aside, breastfeeding did not show significant differences between groups in terms of local recurrences or development of second contralateral breast cancer (adjusted subdistribution hazard ratio, 1.08; P = .82).

“These are the first decidedly encouraging results on the feasibility and safety of breastfeeding after breast cancer in young women with BRCA mutations,” Blondeaux said, noting that the study had a relatively long follow-up period of 7 years but was retrospective in design. Therefore, new results from prospective studies are essential to confirm the data.

Peccatori agreed. “The next important step for the POSITIVE study is precisely the long-term results,” he said.

Toward Reproductive Freedom

The issue of breastfeeding after breast cancer has only recently begun to attract researchers’ attention, as survival rates have become so high as to allow planning a normal reproductive life.

In recent years, numerous studies have demonstrated that pregnancy is possible and safe following breast cancer, even with the use of assisted reproductive technologies.

“We are now taking a further step forward, an important step to try to guarantee all women — including those who have had breast cancer — reproductive freedom: The freedom to choose whether or not to have children,” Peccatori explained, emphasizing the importance of making informed and safe decisions about one’s reproductive life, from conception to breastfeeding.

Breastfeeding is an important complement to pregnancy and motherhood, he explained, but not all women experience motherhood in the same way, and some choose not to breastfeed. “We should never demonize this choice, which is entirely legitimate,” he said. However, it is important not to deny the possibility of breastfeeding to those who wish to do so, simply due to a lack of data.

“The results of the two studies presented at ESMO are particularly useful in this regard and provide the basis for more careful counseling, taking into account the needs of the woman and the child but also the safety of the mother in terms of oncological outcomes,” Blondeaux said.

The data are an important basis for women with a history of cancer who are facing the decision on breastfeeding but are not enough on their own. “For breastfeeding to be a real possibility, there also needs to be social support that includes maternity and breastfeeding protection and active breastfeeding support,” Peccatori said, highlighting the leading roles of midwives or organizations like Italy’s “La Leche League” that can accompany the mother, especially if she has survived breast cancer, along the breastfeeding journey.

The study was funded by the Italian Association for Cancer Research. The POSITIVE study received funds from various public institutions and foundations and several pharmaceutical companies. Peccatori and Blondeaux declared no personal conflicts of interest in relation to this study.

Cristina Ferrario is a molecular biologist and former researcher in molecular oncology at three institutes in Milan. She has a master’s degree in communication and health from the University of Milan, Milan, and a master’s degree in cancer genetics from the University of Pavia, Pavia, Italy. She has worked as a science journalist for more than 20 years.

This story was translated from Univadis Italy using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.