Impact of Clipped Node as a Sentinel Lymph Node on Axillary Staging Following Neoadjuvant Chemotherapy in Clinically Node-Positive Breast Cancer

Background: Residual disease after neoadjuvant chemotherapy (NAC) is prognostic and informs adjuvant treatment. Targeted axillary dissection (TAD) following NAC has low false-negative rates, facilitating accurate axillary staging. This study evaluates the clipped node status in axillary staging utilizing TAD. Methods: Retrospective review identified cN1 breast cancer patients treated with NAC and TAD from July 2013 to June 2023. Nodal ultrasound and biopsy defined cN1 status. Patient, tumor, and treatment characteristics were compared based on clipped node status (sentinel lymph node [SLN] or non-SLN). Multivariate analysis of factors associated with the clipped node as a non-SLN was performed. Results: A total of 680 patients underwent TAD, 94.6% with dual-tracer mapping. In three patients (0.4%), no SLN was identified. The clipped node was a SLN in 610 patients (90%) and non-SLN in 70 (10.3%). When the clipped node was a non-SLN, 42 (60%) were positive for metastasis. In 22 of 42 patients (52%), the clipped non-SLN was the only positive node. The clipped non-SLN cohort had a higher proportion with >3 suspicious nodes at presentation (p = 0.003), fewer SLNs excised (mean 2.2 vs. 3.5, p ≤ 0.001), and fewer positive SLNs (p ≤ 0.001). On multivariate analysis, > 3 suspicious nodes on ultrasound (odds ratio 3.0, p = 0.001) and tumor size at presentation (odds ratio 0.9, p = 0.02) were significantly associated with the clipped node as a non-SLN. Conclusions: When the clipped node was a non-SLN, half of the time it was the only positive node and only residual disease on TAD. Given implications for adjuvant therapy, selective clipped node excision is recommended for precise identification of residual disease after NAC.