Axillary Response to Neoadjuvant Therapy in Node-Positive, Estrogen Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer Patients: Predictors and Oncologic Outcomes

Background One potential benefit of neoadjuvant therapy (NAT) in node-positive, estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2−) patients is axillary downstaging to avoid axillary dissection. Objective The aim of this study was to evaluate axillary response to NAT with chemotherapy (NCT) or endocrine therapy (NET) and identify potential predictors of response. Methods A prospectively collected database was queried for node-positive, ER+, HER2− breast cancer patients treated with NAT and surgery from January 2011 to September 2020. Axillary response was categorized into pathologic complete response (pCR) versus no pCR, and was correlated to demographic and clinicopathologic parameters in a logistic regression model. Results A cohort of 176 eligible patients was identified and 178 breast cancers were included in the study. The overall axillary pCR rate was 12.3% (22/178). NCT and NET achieved response rates of 13.9% (19/137) and 7.3% (3/41), respectively ( p = 0.232). A significantly higher axillary pCR rate was identified in patients with clinical stage II at diagnosis (12/60, 20%) compared with stage III (10/118, 8.4%; p = 0.03). NET patients with ypN0 were younger and were treated for a longer period of time (>6 months). Completion axillary dissection was omitted in the majority (73.7%) of NCT patients achieving axillary pCR. Conclusions For patients with node-positive, ER+, HER2− breast cancer, a lower burden of disease at the time of diagnosis (stage II) is associated with a significantly higher axillary pCR, enabling those patients to be spared axillary dissection. Further studies are necessary to define the role of genomic profiling in predicting axillary response.