Surgical Management of the Axilla in HR+/HER2- Breast Cancer in the Z1071 Era: A Propensity Score-Matched Analysis of the National Cancer Database.

Background: Axillary management varies between sentinel lymph node biopsy (SLNB) and axillary lymph node dissection (ALND) for patients with clinical N1 (cN1), hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)/neu-negative (HER2-), infiltrative ductal carcinoma (IDC) who achieve a complete clinical response (cCR) to neoadjuvant systemic therapy (NAST). This study sought to evaluate clinical practice patterns and survival outcomes of SLNB versus ALND in this patient subset.

Methods: Patients with cN1, HR+/HER2-, unilateral IDC demonstrating a cCR to NAST were identified from the 2012-2017 National Cancer Database (NCDB) and stratified based on final axillary surgery management (SLNB vs ALND). After propensity score-matching, overall survival (OS) was compared using a Kaplan-Meier analysis, and significant OS predictors were identified using Cox regression.

Results: Of the 1676 patients selected for this study, 593 (35.4%) underwent SLNB and 1083 (64.6%) underwent ALND. Use of SLNB increased by 28 % between 2012 and 2017. Among a total of 584 matched patients, 461 matched ypN0 patients, and 108 matched ypN+ patients, mean OS did not differ between SLNB and ALND (all patients [92.1 ± 0.8 vs 90.2 ± 1.0 months; p = 0.157], ypN0 patients [92.4 ± 0.8 vs 89.9 ± 0.9 months; p = 0.105], ypN+ patients [83.5 ± 2.3 vs 91.7 ± 2.7 months; p ± 0.963). Cox regression identified age, Charlson score, clinical T stage, and pathologic nodal status as significant predictors of OS.

Conclusion: The final surgical management strategy used for cN1, HR+/HER2- IDC patients who achieved a cCR to NAST did not have a significant impact on survival outcomes in this analysis. Potential opportunities for de-escalation of axillary management among this patient subset exist, and validation studies are needed.