Breastfeeding after breast cancer is safe
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Women who breastfeed after undergoing treatment for breast cancer are not at elevated risk for recurrence or new breast cancers, two studies presented at ESMO Congress showed.
In one multicenter, retrospective cohort study, researchers evaluated nearly 5,000 female breast cancer survivors aged 40 years or younger who had germline BRCA mutations.
Nearly 25% of women who gave birth during the study period breastfed their babies. Slightly less than half could not breastfeed due to prophylactic bilateral mastectomies.
After median follow-up of 7 years postpartum, results showed no difference in breast cancer recurrences or new breast cancer diagnoses among women who breastfed vs. those who did not (adjusted subdistribution HR = 1.08; 95% CI, 0.57-2.06). DFS and OS rates also appeared comparable between groups.
The second study — the POSITIVE trial — included 518 young women with early hormone receptor-positive breast cancer who temporarily stopped endocrine therapy to attempt pregnancy.
Breastfeeding did not affect breast cancer-free interval (HR = 1.12; 95% CI, 0.28-4.5).
Researchers reported nine events, three of which were local recurrences. At 2 years after the first live birth, cumulative incidence of breast cancer-free interval events appeared comparable between the breastfeeding and non-breastfeeding groups (3.6% vs. 3.1%).
“We’re using this information to educate our patients and let them know that [breastfeeding] is safe, but they may have some challenges,” Ann H. Partridge, MD, MPH, professor of medicine at Harvard Medical School, director of the Adult Survivorship Program at Dana-Farber/Brigham and Women’s Cancer Center, and a researcher on both studies, told Healio. “We’re creating teaching sheets for our patients who want to go on to get pregnant and nurse so they can have tailored guidance. The good news is that it is both safe and feasible.”
Healio spoke with Patridge about the implications of these findings and how they may affect decision-making for women who undergo breast cancer treatment.
Healio: Prior to these studies, what evidence existed regarding the risks for breast cancer recurrence or new cancers after breastfeeding?
Partridge: Very little was known. Most evidence was anecdotal, and there wasn’t much data regarding patient outcomes. The good news is these studies provide a fair bit of new data showing that it does appear safe, whether one has a BRCA mutation or interrupts endocrine therapy for breast cancer. There’s no signal for any kind of detriment in terms of breast cancer outcomes in two very different studies of young women survivors who had babies after breast cancer.
Healio: What new evidence did the POSITIVE trial yield?
Partridge: The POSITIVE trial was a prospective trial in which women were enrolled after taking 18 to 30 months of endocrine therapy. They then came off their endocrine therapy to attempt pregnancy. At median follow-up of 41 months, about 75% had a live birth. Among those who had a live birth, a substantial proportion — about two-thirds — breastfed. We looked at how they breastfed and whether they appeared to do just as well as those who did not breastfeed. Indeed, they did.
Healio: What insights did the other study provide?
Partridge: The second study was a worldwide collaboration looking at BRCA1 and BRCA2 mutation carriers. We assessed several different outcomes. One was having a baby after breast cancer, which we’ve already proven is not associated with detriment. We wanted to find out if women who lactated and nursed did any worse than women who had a baby and didn’t nurse, or women who did not have a baby. The answer is no. We saw no worsening of their outcomes.
Healio: Do these findings have the potential to change the way these women are managed?
Partridge: Yes, this is already happening. We just published a separate prospective cohort study looking at women who had live births. We surveyed them about their nursing experiences. We found that many women were able to breastfeed, but they did have difficulties. Most of them had trouble breastfeeding from the cancer-affected side if they’d had radiation there.
We’re collaborating with patient advocates who have had babies after breast cancer to develop patient-facing materials to better support breast cancer survivors if they choose to go down this path. Nobody wants to do this alone, and there aren’t many people out there teaching breast cancer survivors about how to breastfeed, which can be challenging even for women without a history of cancer.
Healio: Is there anything else you’d like to mention?
Partridge: Breast cancer survivors — and young adult cancer survivors in general — want to live their fullest possible life after cancer. This is another way, through research, that we can assure them that it is reasonable, feasible and safe to try to nurse their baby if they want to. There are some compromises — for example, I am sure some of these women would like to nurse longer, but may have to get back on endocrine therapy. However, otherwise, these studies suggest that there’s no medical reason a woman can’t nurse her baby.
References:
- Azim HA Jr, et al. Abstract 1814O. Presented at ESMO Congress; Sept. 13-17, 2024; Barcelona, Spain.
- Blondeaux E, at al. Abstract 1815O. Presented at ESMO Congress; Sept. 13-17, 2024; Barcelona, Spain.
- ESMO. Studies provide first evidence that breastfeeding after breast cancer is safe (press release). Available at: https://www.esmo.org/newsroom/press-and-media-hub/esmo-media-releases/studies-provide-first-evidence-that-breastfeeding-after-breast-cancer-is-safe. Published Sept. Sept. 9, 2024. Accessed Oct. 17, 2024.
- Sella T, et al. Cancer. 2024; doi:10.1002/cncr.35585.
For more information:
Ann H. Partridge, MD, MPH, can be reached at ann_partridge@dfci.harvard.edu.
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