Omitting sentinel lymph node biopsy (SLNB) in patients with early-stage breast cancer undergoing breast-conserving surgery may not increase the risk for recurrence over 5 years, according to findings presented at San Antonio Breast Cancer Symposium (SABCS) 2025.

The results, from the phase 3 BOOG 2013-08 trial, showed noninferior 5-year regional recurrence and regional recurrence-free survival among patients who skipped SLNB compared with those who underwent the procedure.

The findings indicate that SLNB can be safely skipped in many patients with early-stage breast cancer — especially those with hormone receptor-positive (HR+)/HER2- disease, who constituted most of the study group, said presenter Marjolein Smidt, MD, PhD, of Maastricht University Medical Center in Maastricht, Netherlands.

She noted that omitting SLNB is cost-effective and avoids complications such as lymphedema — which can lead to better quality of life and smoother recovery overall.

At the same time, Smidt and other experts discussing the results at SABCS highlighted an important unknown: Because trial participants underwent whole-breast radiation, it is unclear whether skipping SLNB is equally safe for patients receiving de-escalated radiotherapy approaches.

Supportive Evidence

Over the past two decades, breast cancer care has shifted toward minimizing invasiveness while preserving oncologic safety.

Smidt noted that in early breast cancer, the sentinel node is often negative and previous studies — including the INSEMA trial reported last year at SABCS — have shown that omitting SLNB does not compromise survival in patients with low-risk, early-stage invasive breast cancer undergoing breast-conserving surgery.

The BOOG 2013-08 trial enrolled 1733 women (mean age, 61 years) with unilateral, clinically node-negative cT1-T2 breast cancer (up to 5 cm) undergoing breast-conserving surgery and whole-breast radiation. Most tumors (87%) were HR+/HER2-.

Patients were randomized 1:1 to receive SLNB or omit it. Primary systemic therapy, which included chemotherapy with or without targeted therapy and endocrine therapy, were comparable between groups.

Of the 1733 patients, 749 in the SLNB group and 825 in the no-SLNB group were evaluated at a median follow-up of 5 years.

Median 5-year regional recurrence-free survival was 96.6% in the SLNB group and 94.2% in the no-SLNB group — a difference of 2.35%, which did not exceed the noninferiority margin, Smidt reported.

Distant disease-free survival was96.0% with SLNB and 92.9% without (difference 3.3%).

Smidt noted that most trial participants were aged 50 years or older and had grade 1-2, cT1 tumors. “This indicates that sentinel lymph node biopsy omission may be safely considered in these patients,” she said.

But a key limitation of the study, Smidt said, was reliance on per-protocol analysis, as whole-breast irradiation was a standard practice after breast-conserving surgery at the time when the trial was designed.

“Present-day radiation therapies include protocols that are different, such as partial breast radiation,” she pointed out. “With the data from this trial, we cannot prove that omitting SLNB is also safe when patients are treated with other radiation protocols, but we can try to extrapolate the results in the future.”

De-Escalate Surgery or Radiation?

Experts discussing the findings at a press briefing agreed that omitting SLNB can be a reasonable option in carefully selected low-risk patients but cautioned that the interplay between surgical and radiation de-escalation is not yet fully understood.

It is becoming clear that“we have an option to avoid the sentinel biopsy,” said Gaorav Gupta, MD, PhD, a radiation oncologist at the University of North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina.

However, he added, trials to date have used whole-breast irradiation, while many US centers routinely use partial-breast radiation.

“We don’t yet know if it’s completely safe to omit the sentinel node biopsy in the context of partial-breast radiation in all cases,” Gupta said. “We may need some additional evidence to see how these different de-escalation strategies can interact with each other.”

Isabelle Bedrosian, MD, surgical oncologist at The University of Texas MD Anderson Cancer Center, Houston, echoed concerns about trial heterogeneity and the difficulty of reconciling de-escalation strategies.

“We’re struggling with the fact that we have trials of radiation de-escalation and trials of surgical de-escalation,” she said. “You either omit the axillary surgery but do the whole-breast radiation, or you give the radiation oncologist the axillary staging so he can feel confident in de-escalating radiation.”

Lacking data to clarify the issue, Bedrosian said, “If we de-escalate surgery, we’re kind of committed to doing more radiation because that’s how these trials were done.”

This study was funded by the Dutch Cancer Society, Central Health Insurance, and the Netherlands Organization for Health Research and Development. Smidt and Bedrosian had no disclosures. Gupta disclosed receiving grant/research support from Merck and Breakpoint Therapeutics and royalty payments from Naveris, Inc.