Feasibility and safety of targeted axillary dissection guided by intraoperative ultrasound after neoadjuvant treatment.

Background: Axillary management in cN + axillary nodes after neoadjuvant systemic therapy (NST) in breast cancer (BC) remains under research with the aim of de-escalation of axillary node dissection (ALND). Several axillary guided localization techniques have been reported. This study evaluates the safety of intraoperative ultrasound (IOUS) guided targeted axillary dissection (TAD) in a large sample after the results of ILINA trial.

Materials: Prospective data have been collected from October 2015 to June 2022 in patients with cT0-T4 and positive axillary lymph nodes (cN1) treated with NST. Before NST, an ultrasound visible marker was placed into the positive node. After NST, IOUS guided TAD was performed including sentinel node biopsy (SLN). Until December 2019, all patients underwent an ALND after TAD procedure. From January 2020, ALND was spared in those patients with an axillary pathological complete response (pCR).

Results: 235 patients were included. pCR (ypT0/is ypN0) was achieved in 29% patients. Identification rate (IR) of the clipped node by IOUS was 96% (95% IC, 92.5-98.1%) and IR of SLN was 95% (95% IC, 90.8-97.2%). False negative rate (FNR) for TAD procedure (SLN + clipped node) was 7.0% (95% IC, 2.3-15.7%), which decreased to 4.9% when a total of 3 or more nodes were removed. Axillary ultrasound before surgery assessed residual disease with an AUC of 0.5241. Residual axillary disease tend to be the most significant factor for axillary recurrences.

Conclusions: This study confirms the feasibility, safety and accuracy of IOUS guided surgery for axillary staging after NST in node positive BC patients.