De-escalating axillary surgery in early breast cancer: external validation of a retrospective cohort

BACKGROUND: Sentinel lymph node biopsy (SLNB) is the standard for axillary staging in early breast cancer, yet its relevance is increasingly questioned in patients with favorable tumor biology when nodal status does not influence systemic treatment decisions. METHODS: We conducted a retrospective, single-center observational study including 162 women with clinically and sonographically node-negative (cN0) pT1 invasive breast cancer treated between 2019 and 2024 at a French university hospital. All patients underwent axillary staging and had complete molecular profiling. Among the 25 patients with pathologically positive nodes (pN+), two multidisciplinary team (MDT) discussions were simulated: one blinded to nodal status (limited-information MDT) and one with complete clinicopathologic data (full-information MDT). Recommendations for adjuvant chemotherapy and genomic testing (Oncotype DX) were compared. RESULTS: Most tumors were hormone receptor-positive (90%) and HER2-negative (87%); 9% were triple-negative. Despite negative preoperative axillary ultrasound, nodal involvement was identified in 25 patients (15%). In the limited-information MDT, chemotherapy was recommended in 8 patients and genomic testing in 11 patients. In contrast, the full-information MDT recommended chemotherapy in 16 patients and genomic testing in 9 patients, with 2 additional patients ultimately receiving chemotherapy. Omission of nodal status during MDT deliberation was associated with a significant reduction in chemotherapy recommendations (p < 0.01). Genomic testing contributed to treatment de-escalation in both scenarios. CONCLUSIONS: In selected patients with pT1 breast cancer, omission of axillary nodal status during MDT decision-making may safely reduce adjuvant chemotherapy use without compromising treatment planning, supporting current axillary de-escalation strategies.