Incidence of Positive Sentinel Lymph Node in cN0(f) Breast Cancer Patients After Neoadjuvant Chemotherapy: Opportunity to Defer Intraoperative Frozen Section Analysis

Document Type

Conference Proceeding

Publication Date

3-6-2023

Publication Title

Ann Surg Oncol

Abstract

INTRODUCTION: When NACT is utilized for breast cancer treatment, patients often undergo pretreatment axillary ultrasound with needle biopsy and clip placement . Standard of care surgical management after NACT includes SLN biopsy with intraoperative frozen section analysis, possible axillary lymph node dissection (ALND). Thorough evaluation of SLNs after NACT is imperative to assess for treatment effect which can affect adjuvant systemic and radiotherapy recommendations. We previously defined our institution's rate of ypN1(sn) in cN0 patients following NACT showing frozen section could be avoided in lieu of permanent pathology in hormone receptor (HR) neg/HER2 neg and HR neg/HER2 positive cases; however, due to axillary node needle biopsy false negative (FN) rates ranging from 7-30% in published data, we have continued to perform frozen section in cases with an ultrasound suspicious axillary node biopsied negative for metastasis (cN0(f)). We now aim to define the rate of ypN1(sn) in cN0(f) cases and the incidence of false negative axillary node biopsy in patients who received NACT.

METHODS: Our IRB approved database was queried for cN0(f) cases undergoing NACT from 2016 to 2020, excluding cT4, stage IV, and those that left the system. Patient demographics, clinical characteristics, tumor biology (grade, receptor status, MIB1), and clinical/pathologic staging were recorded. We stratified by HR and HER2 status defined as: HR neg(0%), HR weakly pos(1-10%), HR pos( >11%), HER2 neg(0, 1+, 2+ neg by FISH), HER2 pos(3+, 2+ positive by FISH).

RESULTS: Of the 29 cN0(f) cases, 5 cases were excluded by defined criteria leaving 24 for analysis. All 24 patients that presented as cN0(f) were found to be ypN0(sn) on final surgical pathology. Of these, 5(20.8%) were found to have SLN treatment effect, suggesting presence of missed metastatic disease prior to NACT; 4(80%) were HR neg/HER2 neg or HR weakly pos(≤10%)/ HER2 neg.

CONCLUSIONS: Our results showed all 24(100%) cN0(f) cases were ypN0(sn) after NACT. Despite evidence of an axillary node core biopsy FN rate of 20.8% consistent with published data of 7-30%, 80% of the nodes with treatment effect had more aggressive tumor subtypes (HR neg/HER2 neg and HR weakly pos/HER2 neg). These results suggest that frozen section could be avoided at the time of surgery for cN0(f) cases after NACT in lieu of permanent pathology as the likelihood of finding ypN1(sn) is low, thus not requiring ALND.

Volume

30

First Page

S195

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