The first evidence of breastfeeding being safe and feasible after breast cancer was presented in two international studies at the recent European Society for Medical Oncology (ESMO) Congress 2024.
No increase in recurrence or new breast cancers was observed in women who breastfeed after being treated for breast cancer, the studies found.
The first study looked at breastfeeding after breast cancer in young mothers who carried BReast CAncer (BRCA) susceptibility genes. The international retrospective cohort study included women diagnosed with stage 1-3 invasive breast cancer at age 40 or younger between Jan 2000 and Dec 2020.
Using statistical analysis, the researchers compared whether breast cancer returned and how long individuals lived, with or without cancer, in women with the BRCA gene and those without.
Nearly 5,000 women participated in the study, resulting in 659 pregnancies and 474 women delivering a child. After delivery, 23.2% of the women breastfed for a median duration of five months, 14.4% did not breastfeed and 47.5% were unable to breastfeed due to undergoing a double mastectomy before pregnancy. The remaining participants (14.9%) had unknown breastfeeding status.
After a median follow-up of seven years, there was no significant difference in the number of locoregional or contralateral breast cancer recurrences between women who breastfed and those who did not (adjusted sHR=1.08, 95%CI 0.57-2.06, p=0.82). In addition, breastfeeding had no impact on disease-free survival (adjusted HR=0.83, 95%CI 0.49-1.41, p=0.49) or overall survival (OS), with nine OS events in patients that breastfed and three in those who did not breastfeed.
In the second study, part of the POSITIVE trial, the researchers investigated a secondary endpoint of breastfeeding in women with hormone receptor-positive early breast cancer who had temporarily interrupted treatment to attempt pregnancy after receiving 18-30 months of adjuvant endocrine therapy.
The primary endpoint had been whether this temporary interruption of treatment was safe, and the researchers found no increase in short-term risk of breast cancer events in these women.
At a median follow-up of 41 months, 317 patients had given birth, of whom 196 (62%) breastfed a total of 232 babies.
Breastfeeding did not impact the breast cancer-free interval (BCFI) with few reported events in women who breastfed (n=9/196). Two years after the first live birth, the cumulative incidence of BCFI was 3.6% and 3.1% in the breastfeeding and non-breastfeeding groups, respectively.
It was concluded that while longer follow-up is warranted, both studies provide key evidence for clinicians and women with breast cancer who wish to pursue pregnancy and breastfeed.
Indeed, commenting on the findings, Dr Maria Alice Franzoi, medical oncologist and researcher at Gustave Roussy, Villejuif, France, who was not involved in the studies, said: ‘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 that they are prepared and empowered across the entire breast cancer journey for shared decision making.’
References
Blondeaux, 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; Sept 14, Proffered Paper Session on Saturday, 14 September, 14:45-16:25 (CEST) in the Pamplona Auditorium – Hall 3.
Azim, HA 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; Sept 14, Proffered Paper Session on Saturday, 14 September, 14:45-16:25 (CEST) in the Pamplona Auditorium – Hall 3.
