Neoadjuvant Chemotherapy and Nodal Response Rates in Luminal Breast Cancer: Effects of Age and Tumor Ki67

Background Neoadjuvant chemotherapy (NAC) is standard for most triple-negative and human epidermal growth factor receptor 2 (HER2)+ breast cancers, and frequently downstages node-positive (cN+) disease, permitting omission of axillary dissection. In estrogen receptor (ER)+/HER2– disease, response rates are lower. Whether Ki67 is associated with axillary downstaging in ER+/HER2– disease is unknown. Methods With institutional review board approval, we queried our institutional database to identify all patients with primary ER+/HER2– biopsy-proven cN+ breast cancer treated with NAC followed by surgery from January 2012 to December 2021. Nodal pathologic complete response (pCR) rates were evaluated by pretreatment Ki67 and patient age. Results 315 patients (median age 50 years) were included. Nodal pCR rate was 24.8% (78/315) and was higher in patients aged