Neoadjuvant chemotherapy in HER2-negative luminal breast cancer: surgical decision-making and predictors of pathological complete Response

Abstract

Introduction: Neoadjuvant chemotherapy (NAC) in breast cancer aims to optimize surgical outcomes, though its benefit in luminal HER2-negative patients remains unclear. Objective: To evaluate clinical and radiological responses, identify factors associated with pathological complete response (pCR) and assess their impact on surgical decisions in patients with stage II–III HER2-negative luminal breast cancer treated with NAC. Materials and Methods: This was an observational, retrospective, analytical and cross-sectional study based on a database of consecutive cases diagnosed between 2016 and 2022 at two private oncology centers in Metropolitan Lima. The study included women with HER2-negative luminal breast cancer diagnosed at clinical stages II–III who received NAC (n = 122). Results: The mean age was 46.6 years (range: 25–72). The most frequent clinical stages were IIB (36.9%) and IIIA (35.2%). Ductal histology (90.9%), histologic grade 2 (69.6%), and the Luminal B molecular subtype (60.6%) were the most common characteristics. The clinical-radiological response rate in the breast was 86%. However, rates of radical surgery were high: mastectomy (67.2%) and axillary lymph node dissection (70.5%). The pathological complete response (pCR) rate was 16.4% in the breast and 24.5% in lymph nodes. The combined breast and nodal pCR rate was 13.9%. None of the clinical or pathological variables analyzed were predictive of pCR. Conclusion: In this cohort of patients with HER2-negative luminal breast cancer treated with NAC, a high rate of clinical-radiological
response was observed. However, surgical management was predominantly radical, and pCR rates were low. No clinical or pathological predictors of pCR were identified.