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Background: Management of the axilla in stage II/III breast cancer undergoing neoadjuvant systemic therapy (NST) is controversial. To understand current patterns of care, we collected axillary data from 2 NST trials: HER2-positive (Cancer and Leukemia Group B [CALGB] 40601) and triple-negative (CALGB 40603).Study Design: Axillary evaluation pre- and post-NST was per the treating surgeon and could include sentinel node biopsy. Post-NST, node-positive patients were recommended to undergo axillary lymph node dissection (ALND). We report pre-NST histopathologic nodal evaluation and post-NST axillary surgical procedures with correlation to clinical and pathologic nodal status.Results: Seven hundred and forty-two patients were treated, 704 had complete nodal data pre-NST and post-NST. Pre-NST, 422 (60%) of 704 patients underwent at least 1 procedure for axillary node evaluation (total of 468 procedures): fine needle aspiration (n = 234; 74% positive), core needle biopsy (n = 138; 72% positive), and sentinel node biopsy (n = 96; 33% positive). Pre-NST, 304 patients were considered node-positive. Post-NST, 304 of 704 patients (43%) underwent sentinel node biopsy; 44 were positive and 259 were negative (29 and 36 patients, respectively, had subsequent ALND). Three hundred and ninety-one (56%) patients went directly to post-NST ALND and 9 (1%) pre-NST node-positive patients had no post-NST axillary procedure. Post-NST, 170 (24%) of the 704 patients had residual axillary disease. Agreement between post-NST clinical and radiologic staging and post-NST histologic staging was strongest for node-negative (81%) and weaker for node-positive (N1 31%, N2 29%), with more than half of the clinically node-positive patients found to be pathologic negative (p < 0.001).Conclusions: Our results suggest there is no widely accepted standard for axillary nodal evaluation pre-NST. Post-NST staging was highly concordant in patients with N0 disease, but poorly so in node-positive disease. Accurate methods are needed to identify post-NST patients without residual axillary disease to potentially spare ALND. [ABSTRACT FROM AUTHOR]

Summary: The neoadjuvant setting provides a unique opportunity to study the effect of systemic treatments on breast cancer biology and to identify clinically useful prognostic and predictive biomarkers. Discrepancies and inconsistencies in the use of definitions and endpoint assessments in this setting confound the analysis and interpretation of results across clinical trials and hinder research progress. This Review represents a joint effort of the Breast International Group and the National Cancer Institute-sponsored North American Breast Cancer Group to provide clinicians and researchers with a series of standardised definitions and endpoints that could be implemented in future neoadjuvant clinical trials. Definitions of the setting of interest and of survival endpoints are recommended, together with proposals for standard assessment of the response to treatment, use of functional and molecular imaging endpoints, and characterisation and selection of the population to treat. We expect that implementation of these recommendations will improve the conduct, reporting, and effectiveness of clinical trials and fully exploit the clinical and scientific potential of the neoadjuvant setting in breast cancer. [ABSTRACT FROM AUTHOR]