A multicenter study on efficacy of dual-target neoadjuvant therapy for HER2-positive breast cancer and a consistent analysis of efficacy evaluation of neoadjuvant therapy by Miller-Payne and RCB pathological evaluation systems (CSBrS-026).

Objective: The aim of this study was to investigate the factors influencing pathological complete response (pCR) rate in early breast cancer patients receiving neoadjuvant dual-target [trastuzumab (H) + pertuzumab (P)] therapy combined with chemotherapy. Additionally, the consistency of the Miller-Payne and residual cancer burden (RCB) systems in evaluating the efficacy of neoadjuvant therapy for early human epidermal growth factor receptor-2 (HER2)+ breast cancer was analyzed.

Methods: The clinicopathological data of female patients with early-stage HER2+ breast cancer who received dual-target neoadjuvant therapy at 26 hospitals of the Chinese Society of Breast Surgery (CSBrS) from March 2019 to December 2021 were collected. Patients were allocated to four groups: the HER2 immunohistochemistry (IHC) 3+/hormone receptor (HR)-, IHC3+/HR+, IHC2+ hybridization (ISH)+/HR- and IHC2+ ISH+/HR+ groups. The overall pCR rate for patients, the pCR rate in each group and the factors affecting the pCR rate were analyzed. The consistency between the Miller-Payne and RCB systems in assessing the efficacy of neoadjuvant therapy was analyzed.

Results: From March 1, 2019, to December 31, 2021, 77,376 female patients with early-stage breast cancer were treated at 26 hospitals; 18,853 (24.4%) of these patients were HER2+. After exclusion of unqualified patients, 2,395 patients who received neoadjuvant dual-target (H+P) therapy combined with chemotherapy were included in this study. The overall pCR rate was 53.0%, and the patients' HR statuses and different HER2+ statuses were significantly correlated with the pCR rate (P0.05). The consistency of the pathological efficacy assessed by the Miller-Payne and RCB systems was 88.0% (=0.717, P0.001).

Conclusions: Different HER2 expression statuses and HR expression statuses are correlated with the pCR rate after dual-target neoadjuvant therapy in HER2+ breast cancer patients. There is a relatively good consistency between Miller-Payne and RCB systems in evaluating the pathologic efficacy of neoadjuvant therapy for HER2+ breast cancer.