Outcomes from targeted axillary lymph node dissection after neoadjuvant chemotherapy for breast cancer in a safety-net medical center.

e12608 Background: Prior data from this Center demonstrated that axillary node recurrence was uncommon after targeted axillary dissection for patients who were pathologically node-negative after neoadjuvant chemotherapy (NAC). The current study was done to determine whether results could justify further de-escalation of axillary lymph node dissection (ALND) in selected patients having NAC. Methods: All breast cancer patients treated with NAC from 2015-2023 were included in the study except those with metastatic or inflammatory cancer. Axillary nodes were evaluated with pretreatment ultrasound. Core biopsies with microclip placement were done on abnormal nodes. Technetium-99m sulfur colloid was the mapping agent used for sentinel lymph node dissection (SLND), and clipped nodes were identified using wire localization. Patients who were clinically node-positive (ycN+) post-NAC, did not map, did not have a clipped node retrieved, or had adenopathy identified during SLND were assigned to ALND. Retrospective multi-variable analyses were performed to define associations between clinical features and outcomes. Results: There were 274 predominantly Hispanic (78%) patients, median age 51 years and follow-up 38.1 months. Pre-NAC, 76 patients had a negative axillary ultrasound or core biopsy (cN0) and 198 were pN+. Of 198 pN+ patients, 120 were clinically node-negative (ycN0) post-NAC and had wire-directed (WD) SLND, while 78 were ycN+ and had planned ALND. Forty percent 40% of WD-SLND were ypN+ and 60% converted to ypN0, thus avoiding ALND in 47% of initially node-positive patients. Of 76 patients who were cN0, SLND was ypN+ in10%. Overall, 116 patients had SLND alone and 80 had SLND plus ALND. Of 38 patients with histologically positive lymph nodes at the time of WD-SLND, 22 (58%) had additional positive non-sentinel lymph nodes in the ALND specimen. Final lymph node status (ypN) was ypN1 for 24 (63%) patients, ypN2 for 12 (32%), and ypN3 for 2 (5%). Biomarker subtype, pathologic T-category post-NAC, and radiographic response to NAC were significantly associated with lymph node status at WD-SLND, whereas patient age and focality of tumor were not. Of 11 patients who had WD-SLND and did not map, 8 had the clipped node evaluated, 6 of whom had negative frozen section and 5 were ypN0. Conclusions: ALND was avoided in approximately half of patients who presented with axillary node metastases and became ycN0 post-NAC. Over 50% of patients with a positive lymph node at WD-SLND had additional positive nodes in the ALND specimen. Response to NAC correlated with node status at surgery. Patients who do not map may not need ALND if a pN+ clipped node is retrieved and is ypN0.