According to two international studies presented at the upcoming annual meeting of the European Society for Medical Oncology(ESMO), being held in Barcelona, Spain, September 13-17, 2024, women who breastfeed after receiving treatment for breast cancer, including those with a germline BRCA mutation (an inherited change in BRCA genes that significantly increases the risk of developing certain cancers, especially breast cancer), do not face an increased risk of recurrence or developing new breast cancers. [1][2]
“Our study provides the first evidence on the safety of breastfeeding after breast cancer in young women carrying a germline BRCA mutation,” said Eva Blondeaux, MD, Oncologist, IRCCS Ospedale Policlinico San Martino, Genova, Italy, who will present one of the studies. [1]
“This indicates the possibility for these women to achieve a balance between the needs of the mother and those of the baby,” Blondeaux added.
Given the hormone-driven nature of breast cancer, there were previously concerns about pregnancy and breastfeeding after the disease, as both involve changes in hormone levels. This was particularly true for women with the BRCA mutation, who remain at high risk of developing a second breast cancer in the other breast. Recent studies demonstrated that neither assisted reproduction treatments (ART) in young women with high-risk genes, including women carrying a germline BRCA mutation, who have survived breast cancer, [3] nor pregnancy, is associated with an increased risk of recurrence or new cases of breast cancer, [4] until now very little evidence was available on the feasibility and safety of breastfeeding in these women.
Assisted reproduction treatments
Fertility is a major concern for women developing breast cancer at a young age before they have had children because treatment can stop the ovaries from working and trigger menopause.
One way a woman can preserve her fertility is to freeze oocytes (eggs) or embryos before starting breast cancer treatment. [5] These techniques generally involve the use of fertility drugs to stimulate the ovaries to produce eggs, but this increases levels of the hormone estrogen.
“The main take-home message from this study, which analyzed data for nearly 5000 women with BRCA1/2 pathogenic variants who were diagnosed with breast cancer aged 40 years or younger at 78 cancer centers across the world between 2000 and 2020, is that there is no increased risk of breast cancer recurrence with assisted reproductive techniques in young women with BRCA pathogenic variants having a pregnancy after breast cancer. We also found that these procedures are safe for the baby: having a pregnancy with the use of fertility procedures does not increase the risk of complications,” explained Matteo Lambertini, MD, Associate Professor and Consultant in Medical Oncology at the University of Genova, and IRCCS Policlinico San Martino Hospital, Genova, Italy. [6]
Breastfeeding
“I hope these new findings will improve the way we counsel these patients,” said Blondeaux.
The international study followed nearly 5,000 young women carrying a germline BRCA mutation who had survived breast cancer. Nearly one in four of the 474 women who subsequently gave birth breastfed their baby; just under half were unable to breastfeed because they had had both breasts removed to reduce their future cancer risk. After a median follow-up of seven years from giving birth there was no difference in the number of breast cancer recurrences or new breast cancers in women who breastfed their baby compared to those who did not breastfeed (adjusted subdistribution hazard ratio 1.08, 95% confidence interval 0.57-2.06, p=0.82).
There was also no difference in disease-free survival or overall survival.
Beyond BRCA
A second new study that expands the investigation beyond BRCA, addressing women with hormone receptor-positive early breast cancer showed similar results, with no risks associated with breastfeeding. [2]
“These results are key for women who wish to become pregnant and breastfeed their baby after breast cancer,” explained Fedro Alessandro Peccatori, MD, Director of the Fertility & Procreation Unit at the European Institute of Oncology IRCCS, Milan, Italy, a co-author of the study.
“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,” he stressed.
“Doctors 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,” Peccatori said.
POSITIVE study
The POSITIVE study, an international, single-arm, prospective trial included 518 women who temporarily interrupted their breast cancer treatment to have a baby; 317 had at least one live birth and nearly two in three of them breastfed (62%). At two years from the first live birth, the proportion of women with breast cancer recurrence or new breast cancer was similar in those who breastfed (3.6%) as in those who did not breastfeed (3.1%).
“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 healthcare 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,” said Maria Alice Franzoi, MD, medical oncologist and researcher at Gustave Roussy, Villejuif, France, who was not involved in the study.
However, Franzoi cautioned that follow-up of the studies should, ideally, continue for longer.
“Data from these two studies will be extremely useful to guide our practical discussions with young women diagnosed with breast cancer,” Franzoi continued. “We should start thinking and discussing survivorship care planning – including fertility preservation, pregnancy, and breastfeeding for women who want to consider these options – at the time of diagnosis so that they are prepared and empowered across the entire breast cancer journey for shared decision making,” Franzoi concluded.
Clinical Trials
Safety of Pregnancy in BRCA Mutated Breast Cancer Patients – ClinicalTrials.gov ID NCT03673306
Pregnancy Outcome and Safety of Interrupting Therapy for Women With Endocrine Responsive Breast Cancer (POSITIVE) – ClinicalTrials.gov ID NCT02308085
Reference
[1] Blondeaux E, Delucchi V, Mariamidze E et al. Breastfeeding after breast cancer in young BRCA carriers: results from an international cohort study. Abstract 1815O, presented at the ESMO Congress 2024 (13-17 September), Proffered Paper Session on Saturday, 14 September, 14:45-16:25 (CEST) in the Pamplona Auditorium – Hall 3.
[2] Azim HA, Niman S, Partridge AH 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. presented at the ESMO Congress 2024 (13-17 September), Proffered Paper Session on Saturday, 14 September, 14:45-16:25 (CEST) in the Pamplona Auditorium – Hall 3.
[3] Lambertini M, Magaton IM, Hamy-Petit A-S et al. Safety of assisted reproductive techniques in young BRCA carriers with a pregnancy after breast cancer: results from an international cohort study. Abstract 266O presented at ESMO Breast Cancer 2024.
[4] Partridge AH, Niman SM, Ruggeri M et al. Interrupting endocrine therapy to attempt pregnancy after breast cancer. NEJM 2023; 388: 1645-1656
[5] Lambertini M, Blondeaux E, Agostinetto E et al. Pregnancy after breast cancer in young BRCA carriers. An international hospital-based cohort study. JAMA 2024; 331: 49-59
[6] Lambertini M, Magaton IM, Hamy-Petit A-S et al. Safety of assisted reproductive techniques in young BRCA carriers with a pregnancy after breast cancer: results from an international cohort study. Abstract 266O. ESMO Breast Cancer 2024.
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