The Add-On Effect of Fluorouracil, Epirubicin, and Cyclophosphamide Regimens for Neoadjuvant Chemotherapy in Human Epidermal Receptor 2 (HER2)-Positive Breast Cancer: A Single-Center Retrospective Study

Background: The addition of pertuzumab to trastuzumab in neoadjuvant chemotherapy (NAC) for anti-human epidermal receptor 2 (HER2) positive breast cancer has shown a significant improvement in the pathologic complete response (pCR) rate. However, the add-on effect of an anthracycline-based regimen (standard-of-care regimen) remains unclear. In this retrospective, observational study, participants received pertuzumab combination therapy as NAC for HER2-positive primary breast cancer. Methods: This study was conducted from January 1, 2020, to December 31, 2022. Patients who had not received at least three courses of pertuzumab owing to adverse events or those who had received preoperative radiotherapy were excluded. Results: The pCR rate was 35.3% (12/34 patients). The pCR group had a significantly higher percentage of histopathologic grade III (1/11 patients, p=0.030) and a significantly higher percentage of hormone receptor-negative patients (7/12 patients, p=0.015) than the non-pCR group. The non-pCR group had a significantly higher incidence of vascular invasion than the pCR group (7/22 patients, p=0.036). Menopausal status, stage, and ki-67 values were not significantly different between the two groups. Conclusions: This study suggests an unlikely add-on effect of an anthracycline-based regimen for NAC in HER2-positive breast cancer. Moreover, our results support that the pCR rate is high in patients with hormone receptor-negative, HER2-positive breast cancer.