September 16, 2024
By Catlin Nalley
Researchers found that breastfeeding was feasible for the majority of patients with hormone receptor-positive breast cancer who gave birth in the POSITIVE trial. Nearly two-thirds breastfed and more than 50 percent did so for more than 4 months, according to findings presented during ESMO 2024 Congress in Barcelona (Abstract 1814O).
“These results are key for women who wish to become pregnant and breastfeed their baby after breast cancer,” said study co-author Fedro Alessandro Peccatori, MD, PhD, Director of the Fertility & Procreation Unit at the European Institute of Oncology IRCCS in Milan, Italy.
“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.”
Breast cancer is the most common cancer in reproductive age women, with approximately 50,000 new cases each year in Europe and many more worldwide, noted Peccatori, while highlighting that young breast cancer survivors face a number of challenges, including a worse survival compared to their older counterparts.
“The safety of pregnancy after hormone receptor-positive breast cancer has been described, mostly in retrospective studies, but few are available about feasibility and safety of breastfeeding after breast cancer,” he stated. “Here, we present the breastfeeding outcomes in POSITIVE, a key secondary endpoint.”
A prospective, multicenter, single-arm trial, POSITIVE included women 42 years of age or younger with hormone receptor-positive, Stage 1-3 breast cancer who had received adjuvant endocrine therapy for 18-30 months and desired pregnancy. The study showed there was no increase in the short-term risk of breast cancer events among women who opted to temporarily interrupt treatment to attempt pregnancy (N Engl J Med 2023;388:1645-56).
In the current analysis, recently presented at ESMO 2024, the researchers took a closer look at the secondary endpoint of POSITIVE—breastfeeding. The evaluable dataset included women who had at least one live birth on study.
“Here we describe breastfeeding frequency, duration, and laterality, and estimate the cumulative incidence of breast cancer events by breastfeeding status,” noted Peccatori and colleagues. “For this analysis, we recalculated breast cancer-free interval (BCFI) from the date of first live birth to first invasive local, regional, or distant breast cancer recurrence or contralateral breast cancer.”
Among the 518 patients enrolled in the POSITIVE trial, 317 patients gave birth at a median follow-up of 41 months. Of those, 196 (62.6%) breastfed and 16 percent breastfed more than one child. A total of 130 (66.3%) patients breastfed after conservative surgery, according to Peccatori, who noted that breastfeeding was from the contralateral breast in all but two patients while only 38 patients breastfed from both breasts. Sixty-six patients (33.6%) had unilateral mastectomy and breastfed from the contralateral breast.
The investigators identified several factors associated with greater proportion of breastfeeding among the study participants. This included breast-conserving surgery versus unilateral mastectomy (77.8% vs. 45.2%); age ≥35 years (67.6% vs. 55.7%); nulliparity versus parity prior to POSITIVE live birth (66.4% vs. 48.5%); and enrollment region.
Peccatori reported a median duration of breastfeeding for the first child of 4.4 months. Data showed that 37.1 percent of patients breastfed for ≥6 months; 12.8 percent for ≥12 months; and 1.5 percent for ≥24 months.
The investigators found that breastfeeding did not impact the breast cancer free interval with very few breast cancer events reported. Overall, Peccatori and colleagues observed nine BCFI events, including three local recurrences. At 2 years from the first live birth, the cumulative incidence of BCFI in the breastfeeding and non-breastfeeding groups was 3.6 percent and 3.1 percent, respectively.
While summarizing his team’s research, Peccatori noted this study is the “largest prospective evaluation of breastfeeding frequency, pattern, and impact on breast cancer-free interval in a cohort of young patients with HR-positive, early breast cancer.
“The take-home message to me is that breastfeeding is possible for the majority of patients that want to breastfeed, at least in this collective group of patients, and appeared safe at least in the early follow-up,” he concluded. “These data indeed underline the interest of young breast cancer survivors in breastfeeding and the importance of breastfeeding counseling for each and every patient.”
Catlin Nalley is a contributing writer.