Motherhood among breast cancer survivors: Studies provide reassuring evidence on breastfeeding

For new mothers who have undergone breast cancer treatment, including those who harbour the BRCA gene mutation, breastfeeding appears to be a safe and viable option, posing no increased risk of recurrence or development of new breast cancers, according to new research.

Young BRCA carriers

In the first study involving young breast cancer survivors with a germline BRCA mutation (median age at index diagnosis 30 years), the cumulative incidence of locoregional and/or contra lateral breast cancer events over a median follow-up of 7 years after delivery did not significantly diff er between women who did and did not breastfeed (29 percent vs 37 percent; adjusted sub distribution hazard ratio [sHR], 1.08, 95 percent confidence interval [CI], 0.57–2.06; p=0.818). [ESMO 2024, abstract 1815O]

The results were consistent in the subgroup analyses defined by specific BRCA gene (BRCA1 vs BRCA2: p=0.840), interval of pregnancy (≤5 vs >5 years: p=0.116), and hormone receptor status (ER– and/or PR– vs ER+ and PR+: p=0.768), as well as use of chemotherapy (no vs yes: p=0.284), suggesting that breastfeeding did not appear to have a different as sociation with locoregional and/or contralateral breast cancer events in the subgroups explored, noted first study author Dr Eva Blondeaux from the IRCCS Ospedale Policlinico San Martino, Genova, Italy.

Likewise, breastfeeding had no impact on disease-free survival (adjusted HR, 0.83, 95 percent CI, 0.49–1.41; p=0.492) or overall survival. There were nine OS events in the breastfeeding group and three in the non-breastfeeding group. Blondeaux acknowledged that the small number of OS events prevented her team from making formal statistical comparison.

“Our study provides the first evidence on the safety of breastfeeding after breast cancer in young women carrying a germline BRCA mutation,” Blondeaux said. “Our findings emphasize the possibility of achieving a balance between maternal and infant needs without compromising oncological safety.”

A total of 4,732 women from 78 participating centres across 26 countries were enrolled in this study. Of the 659 women who conceived after a breast cancer diagnosis, 474 had a live birth. After delivery, 110 (23.2 percent) women breastfed (median duration 5 months), 68 (14.4 percent) did not breastfeed, 225 (47.5 percent) underwent bilateral risk-reducing mastectomy before delivery and were thus unable to breastfeed, and 71 (15 percent) had unknown breastfeeding status.

Compared with the group who did not breastfeed, the breastfeeding group had more participants who were nulliparous at index diagnosis (61.8 percent vs 45.6 percent; p=0.026) and reported no history of smoking (71.8 percent vs 57.4 per cent; p=0.019). Furthermore, patients with singleton pregnancy were more likely to opt for breastfeeding. Other patient characteristics and treatment patterns were similar between groups.

Women with HR+ breast cancer

Similar results were observed in a secondary analysis of the POSITIVE trial, which expanded the investigation beyond BRCA and included women with HR+ early breast cancer who conceived after temporary interruption of endocrine therapy (ET). [ESMO 2024, abstract 1814O]

“Overall, very few breast cancer-free interval (BCFI) events were observed in the trial – there were only nine events, including three recurrences,” said senior study investigator Dr Fedro Peccatori, Director of the Fertility and Procreation Unit within the Division of Gynecologic Oncology at the European Institute of Oncology IRCCS, Milan, Italy.

BCFI did not significantly diff er between the groups who did and did not breastfeed at 12 (1.1 percent vs 1.9 percent) and 24 months (3.6 percent vs 3.1 percent), indicating that breast feeding had no substantial impact on BCFI (HR, 1.12, 95 per cent CI, 0.28–4.5), Pecatori noted. BCFI was defi ned as the months from first live birth to the first invasive local, regional, or distant breast cancer recurrence or contralateral disease.

The takeaway, according to Pecatori, is that breastfeeding is possible for the majority of breast cancer patients.

“These data underline the interest of young breast cancer survivors in breastfeeding and reinforce the notion that breast feeding counselling should be incorporated into their individualized support,” said Pecatori. “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.”

The POSITIVE trial enrolled 518 patients aged ≤42 years who had HR+ stage I–III breast cancer who had undergone 18–30 months of ET, and desired to become pregnant. The study protocol specified that patients stop ET within a month before enrolment, with a 3-month washout period before attempting pregnancy. ET was interrupted for up to 2 years to allow for attempting pregnancy, conception (or failure to conceive), delivery, and breastfeeding (if desired and if feasible). The patients were strongly recommended to resume ET after 2 years to complete the planned 5–10 years of treatment.

A total of 317 patients had a live birth, for a total of 232 babies. Of these, 196 opted to breastfeed, mostly from the contralateral breast, for a median duration of 4.4 months. Breastfeeding was more likely among patients older than 35 years (62.8 percent vs 51.2 percent), those with no prior children (85.4 percent vs 71.7 percent), and those who underwent breast-conserving surgery (66.3 percent vs 30.6 percent).

Duration of prior ET and time from enrolment to first live birth were not associated with breastfeeding frequency or duration.

Empowering patients, physicians

In a separate news release, study discussant Dr Maria Alice Franzoi from Gustave Roussy, Villejuif, France, described the results of the two studies as encouraging. “The studies significantly enhance the quality of available data and will be valuable in guiding patient-centred decision-making in clinical settings. We should empower both patients and providers with the feasibility and safety data from these studies to encourage early discussions in the care pathway.”

“Ideally, women should receive counselling both before (starting at diagnosis) and after pregnancy. For young women with BRCA mutation-positive disease, the option of delaying prophylactic bilateral mastectomy for those who wish to become pregnant and breastfeed should be part of the shared decision-making process,” Franzoi continued.

Additionally, Franzoi believed that breastfeeding could serve as a healing experience, helping restore a sense of normalcy and bodily function for women after breast cancer. This experience, she added, can facilitate reintegration into social and family life, in addition to strengthening the bond with the child, which should be properly evaluated in future prospective studies.