Axillary dissection for low-volume nodal involvement after neoadjuvant therapy in breast cancer: Multicentre AXSANA cohort study

Background Completion axillary lymph node dissection (cALND) is often recommended for patients with isolated tumour cells (ITCs) or micrometastases in the sentinel lymph node (SLN) or target lymph node (TLN) to assess the definite nodal tumour burden after neoadjuvant chemotherapy (NACT). The aim of this study was to investigate the upgrade of N stage by cALND in patients with low-volume metastases in the SLN/TLN after NACT from the prospective, international, multicentre AXSANA cohort study. Methods NACT-treated patients that converted from a positive to a negative clinical lymph node status and underwent cALND based on low-volume SLN/TLN involvement were included. The association between the final N stage, the pathological tumour response in the breast, and the clinical impact of cALND on post-NACT treatment decisions was determined. Results Among 5329 patients recruited between June 2020 and March 2024, 2194 were scheduled for SLN biopsy (SLNB), targeted axillary dissection (TAD), or TLN biopsy (TLNB). Among 16 patients with ypN0i+(SLN/TLN), one patient was upgraded to ypN1a by cALND, while five of the 71 patients with ypN1mi(SLN/TLN) were upstaged to ypN2 and one of the 71 patients with ypN1mi(SLN/TLN) was upstaged to ypN3. None of these patients had a pCR in the breast and thus nodal upstaging had no impact on post-NACT treatment decisions. Conclusion Despite substantial additional nodal involvement in low-volume SLN/TLN disease, cALND does not provide clinically meaningful information for post-NACT systemic treatment modifications and should not be encouraged for diagnostic purposes alone.