Background: This feasibility study was designed to evaluate if contrast-enhanced ultrasound (CEUS) can identify node-positive patients before neoadjuvant chemotherapy (NACT) and assess the residual cancer burden within the axilla following NACT and therefore, potentially tailor the surgical treatment of the axilla.

Methods: 32 patients were identified of which 26 met the inclusion criteria and underwent CEUS pre and post NACT. The sentinel lymph nodes (SLNs) identified during CEUS were biopsied and clipped. All 26 participants of this study underwent axillary node clearance (ANC) along with breast conservative surgery or mastectomy. Axillary specimens were further reviewed considering the number of positive nodes and if nodes clipped during CEUS were positive or negative.

Results: Following NACT, among the 26 participants, CEUS identified positive SLNs in 8 patients. Post ANC, histology showed that 7/8 of these patients had positive nodes. The remaining 18 patients were found to be node negative on CEUS post NACT. Furthermore, post ANC, the histology of 12 of these patients showed positive nodes with a tumour burden ranging from 1 to 18 LNs. Further analysis showed that in 25% of these patients the identified positive nodes were non SLNs.

Conclusions: The study shows that although the SLN maybe negative post NACT that non-SLNs may still be malignant and therefore a negative SLN does not translate into a negative axillary clearance. Therefore further studies looking at the role of targeted axillary dissection such as the ATNEC trial are important to support de-escalation of axillary surgery in the context of NACT.

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