Women who breastfeed after treatment for breast cancer—including those with germline BRCA-mutated disease—may not be at increased risk of cancer recurrence or new breast cancers, according to two recent international studies presented by Blondeaux et al (Abstract 1815O) and Peccatori et al (Abstract 1814O) at the European Society for Medical Oncology (ESMO) Congress 2024.
Background
Because of the hormone-driven nature of breast cancer, there have previously been concerns regarding pregnancy and breastfeeding after breast cancer treatment, since both involve changes in hormone levels. This may be particularly true among women with the BRCA mutation, who remain at high risk of developing a second breast cancer in the other breast.
Although recent studies have demonstrated that assisted reproduction treatments and pregnancy may not be associated with an increased risk of cancer recurrence or new breast cancers—including in women with a germline BRCA mutation—little evidence is available on the feasibility and safety of breastfeeding in these patients.
“Our study provides the first evidence on the safety of breastfeeding after breast cancer in young women carrying a germline BRCA mutation,” highlighted lead study author of the first study Eva Blondeaux, MD, an oncologist at the Scientific Institute for Research, Hospitalization, and Health Care (IRCCS) Ospedale Policlinico San Martino in Genova, Italy. “This indicates the possibility for these women to achieve a balance between the needs of the mother and those of the baby,” she continued.
Findings From the First Study
In the first study, Dr. Blondeaux and colleagues examined the outcomes of 5,000 young female breast cancer survivors with a germline BRCA mutation. They noted that nearly 25% of the 474 women who subsequently gave birth breastfed their babies; however, just under 50% of them were unable to breastfeed because they had undergone a bilateral mastectomy to reduce their future risk of breast cancer.
After a median follow-up of 7 years from giving birth, there were no statistically significant differences in the number of breast cancer recurrences or new breast cancers between the women who breastfed and those who did not breastfeed (adjusted subdistribution hazard ratio = 1.08, 95% confidence interval = 0.57–2.06, P = .82). There were also no statistically significant differences in disease-free survival or overall survival between the two groups.
Findings From the Second Study
In the second study, the POSITIVE trial, researchers expanded the investigation beyond germline BRCA mutations to address women with early-stage, hormone receptor–positive breast cancer. They recruited 518 women who temporarily interrupted their breast cancer treatment to have a baby—317 of whom had at least one live birth and 62% of whom breastfed.
The researchers found that these patients showed comparable results as those involved in the first study, with no risks associated with breastfeeding. At 2 years from the first live birth, the proportion of women with breast cancer recurrence or new breast cancer was similar in those who breastfed compared with those who did not breastfeed (3.6% vs 3.1%, respectively).
Conclusions
“These results are key for women who wish to become pregnant and breastfeed their baby after breast cancer. It’s time to start thinking of breast cancer survivors as women with all the rights, needs, and possibilities of women who never had cancer,” emphasized co–study author of the second study Fedro Alessandro Peccatori, MD, PhD, Director of the Fertility & Procreation Unit at the European Institute of Oncology IRCCS in Milan, Italy. “[Physicians] were worried to give these women the chance of having a baby, but we have recently shown that this is safe in the short term. Now, with this new information, we can debunk the myth that breastfeeding is neither possible nor safe for breast cancer survivors. They can have a normal pregnancy and relationship with their baby, including breastfeeding,” he underscored.
The researchers indicated that additional longer follow-up studies will be needed to better understand the results.
“There was previously a lack of high-quality data regarding the feasibility and safety of breastfeeding in young women who have been treated for breast cancer. Until now, women and health-care providers lacked information on whether breastfeeding is feasible after breast cancer surgery, on the safety of pausing adjuvant treatments for breastfeeding and on the hormonal changes related to it,” stressed Maria Alice Franzoi, MD, a medical oncologist and researcher at Gustave Roussy in Villejuif, France, who was not involved in these studies. “Data from these two studies will be extremely useful to guide our practical discussions with young women diagnosed with breast cancer. We should start thinking and discussing about survivorship care planning—including fertility preservation, pregnancy, and breastfeeding for women who want to consider these options—at the time of diagnosis, so they are prepared and empowered across the entire breast cancer journey for shared decision-making,” she concluded.
Disclosure: For full disclosures of the study authors, visit cslide.ctimeetingtech.com.
