Neoadjuvant Chemotherapy and Pathologic Complete Response in HR+/HER2− Breast Cancer: Impact of Tumor Ki67 and ER Status

Abstract

Introduction: Neoadjuvant chemotherapy (NAC) is extensively employed in breast cancer (BC), primarily for aggressive subtypes like triple-negative and human epidermal growth factor receptor 2 (HER2)-positive BC and in estrogen receptor-positive (ER+)/HER2− BC with high-risk features. In ER+/HER2− BC, pathological complete rates are much lower (Methods: Retrospective data analysis from Kartal Dr. Lütfi Kırdar City Hospital included HR+/HER2− BC patients who received NAC. Clinicopathological factors, NAC response, and surgical outcomes were assessed. Statistical analyses evaluated the association between Ki67, ER status, and pCR. Results: Of 203 patients, 11.8% achieved pCR. Ki67 (p p p = 0.003, HR: 1.02) and ER percentage (p = 0.019, HR: 0.97) as independent predictors of pCR probability. Conclusion: Consideration of Ki67 and ER percentage aids in NAC decisions for HR+/HER2− BC, identifying patients with high NAC response rates, facilitating axillary preservation, and potentially avoiding axillary dissection. The pCR rates in patients with Ki67 ≤24 are particularly low, especially in patients with a high ER percentage. In these cases, upfront surgery and adjuvant treatment should be considered instead of NAC.