BARCELONA, Spain — When women with breast cancer have one or two positive sentinel lymph nodes after neoadjuvant therapy, axillary radiotherapy (ART) could be as good a choice as axillary lymph node dissection (ALND), according to preliminary data presented at the 15th European Breast Cancer Conference.

Results from the pilot phase of the ongoing phase 3 ADARNAT trial showed that patients had similar oncologic outcomes at 2 years whether they’d undergone ART or ALND after neoadjuvant endocrine therapy or chemotherapy.

There was also a trend toward a lower incidence of lymphedema among women who received ART (18.9%) than among those in the ALND group (26.7%), reported senior researcher Amparo García-Tejedor, MD, of Bellvitge University Hospital and the Catalan Institute of Oncology in Barcelona, Spain.

Although it is too early to say whether ART is noninferior to ALND, the findings suggest that ART could be “a useful tool for axillary de-escalation,” García-Tejedor said.

She and her team are now seeking additional funding so that the main phase of the trial can be completed.

For now, the preliminary findings are encouraging and provide “a sound basis” for the trial to proceed, according to Isabel Rubio, MD, director of the breast pathology unit at Clínica Universidad de Navarra in Madrid, Spain.

Rubio, who was not involved in the trial, noted in a press release that “surgical treatment for breast cancer has already moved towards de-escalation, with many patients now able to avoid full axillary lymph node dissection and its associated side effects.”

She added, however, that patients still face a significant risk for lymphedema after axillary radiation, and future work should try to identify those who may not need either axillary dissection or radiotherapy — “thereby helping to minimize treatment-related complications while maintaining excellent cancer outcomes.”

Evidence for ALND Alternative Lacking

Studies have established ART as an alternative to ALND for patients undergoing surgery as their initial breast cancer treatment. But evidence is lacking on patients who receive neoadjuvant therapy, García-Tejedor said, and axillary dissection remains the guideline-recommended approach.

ADARNAT is a prospective, multicenter, open-label clinical trial designed to assess whether ART is noninferior to ALND in terms of recurrence and overall survival and whether it reduces adverse effects commonly associated with surgery.

Eligible patients had cT1-cT4b disease treated with neoadjuvant chemotherapy or endocrine therapy and had one or two positive sentinel nodes at surgery. They were randomized to ART or ALND.

As of February 2026, around 600 women of a target of 1600 have been recruited across 55 hospitals in Spain and seven in Australia. The primary outcome is the 5-year recurrence of micro- or macrometastatic disease in the axilla determined by clinical and radiologic examination. Secondary outcomes include lymphedema and arm dysfunction, quality of life, disease-free survival, and overall survival.

The findings García-Tejedor presented were from the pilot phase involving 46 patients in the ART arm and 56 in the ALND arm.

Those randomly assigned to ART received radiotherapy targeted to the low-to-mid axillary lymph nodes (levels I-II). Higher nodes (level III and supra nodes), the breast or chest wall, and internal mammary nodes were targeted when indicated. The latter could also be used in the ALND group when needed.

At a median of 2 years, there were no local recurrences in the ART group and one in the ALND group. There were two (4.4%) and three (5.5%) cases of distant metastases in each group, respectively. Two patients in the ALND arm had died — one due to cancer progression and the other due to the development of a second tumor.

Safety findings were presented separately by Maria Laplana-Torres, MD, a radiation oncologist at Hospital Clinic de Barcelona, Barcelona.

She said that although the lymphedema rate was numerically lower in the ART vs ALND arm, the rate of acute skin toxicity (grade 2-3 dermatitis) was significantly higher with radiotherapy (27.8% vs 13.3%).

In addition, more patients in the ART group reported arm mobility limitations — 29.7% vs 17.8% of patients who underwent ALND. Those symptoms, Laplana-Torres said, were predominantly mild and transient, and overall, patients in the two treatment groups reported comparable quality of life, with a “favorable trend” in the ART arm.

Study discussant Philip Poortmans, MD, PhD, of the Iridium Kankernetwerk and University of Antwerp in Antwerp, Belgium, noted that ART is already being favored over ALND in daily practice for certain patients — meaning that clinical practice is currently “outrunning evidence-based medicine.”

The results of ADARNAT and other trials, he said, are much needed and “hopefully will confirm what we are doing now in current practice.”

ADARNAT was supported by the Bellvitge University Hospital and the Spanish breast cancer patient advocacy association, DACMA. García-Tejedor, Laplana-Torres, Rubio, and Poortmans reported having no relevant financial relationships.

Sara Freeman is a medical journalist based in London, England.