Two international studies presented at the ESMO Congress 2024 have confirmed that women who breastfeed after undergoing treatment for breast cancer, including those with germline BRCA mutations, do not face an increased risk of cancer recurrence or the development of new breast cancers.
Dr. Eva Blondeaux, an oncologist at IRCCS Ospedale Policlinico San Martino in Genoa, Italy, who will present one of the studies, stated, “Our study provides the first evidence on the safety of breastfeeding after breast cancer in young women carrying a germline BRCA mutation. This indicates the possibility for these women to achieve a balance between the needs of the mother and those of the baby.”
Historically, concerns about the safety of pregnancy and breastfeeding have persisted due to the hormone-driven nature of breast cancer. Women with BRCA mutations are at a heightened risk for developing a second breast cancer. However, recent studies have indicated that assisted reproductive treatments and pregnancy do not increase the risk of recurrence or new breast cancer cases in these women. Until now, there has been limited evidence regarding the safety and feasibility of breastfeeding for breast cancer survivors.
Dr. Blondeaux expressed hope that these new findings will enhance the counseling provided to patients regarding their options post-treatment.
The international study monitored nearly 5,000 young women with germline BRCA mutations who had survived breast cancer. Among the 474 women who subsequently gave birth, nearly 25% breastfed their babies. Just under half of the participants were unable to breastfeed due to having undergone bilateral mastectomies to mitigate future cancer risks. After a median follow-up of seven years post-delivery, the study found no significant differences in breast cancer recurrence or the emergence of new breast cancers between those who breastfed and those who did not (adjusted subdistribution hazard ratio 1.08, 95% confidence interval 0.57-2.06, p=0.82). Additionally, there were no differences in disease-free survival or overall survival rates.
A second study, which included women with hormone receptor-positive early breast cancer, corroborated these findings, showing no associated risks with breastfeeding.
Dr. Fedro Alessandro Peccatori, Director of the Fertility & Procreation Unit at the European Institute of Oncology IRCCS in Milan and co-author of the study, emphasized the significance of these results for women wishing to become pregnant and breastfeed after experiencing breast cancer. “It’s time to start thinking of breast cancer survivors as women with all the rights, needs, and possibilities of women who have never had cancer,” he stated. “Doctors were previously hesitant to support these women in their desire to have children, but we have demonstrated that having a baby is safe in the short term. Now, we can debunk the myth that breastfeeding is neither possible nor safe for breast cancer survivors.”
The international POSITIVE study involved 518 women who temporarily paused their breast cancer treatment to have a baby; of these, 317 had at least one live birth, and nearly 62% of them breastfed. After two years from the first live birth, the rates of breast cancer recurrence or new cases were similar between those who breastfed (3.6%) and those who did not (3.1%).
Dr. Maria Alice Franzoi, a medical oncologist and researcher at Gustave Roussy in Villejuif, France, who was not involved in the study, commented on the significance of these findings. “There has been a lack of high-quality data regarding the feasibility and safety of breastfeeding in young women treated for breast cancer. Until now, both patients and healthcare providers have lacked information on the safety of breastfeeding after surgery and the implications of pausing adjuvant treatments during that time,” she explained. However, she cautioned that long-term follow-up of these studies is essential.
“Data from these two studies will be extremely useful in guiding our practical discussions with young women diagnosed with breast cancer,” Dr. Franzoi added. “We should begin addressing survivorship care planning—including fertility preservation, pregnancy, and breastfeeding—at the time of diagnosis so that women are prepared and empowered throughout their breast cancer journey.”
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