Neoadjuvant chemotherapy using nanoparticle albumin-bound paclitaxel plus trastuzumab and pertuzumab followed by epirubicin and cyclophosphamide for operable HER2-positive primary breast cancer: a multicenter phase II clinical trial (PerSeUS-BC04)

Background Nanoparticle albumin-bound paclitaxel (nab-PTX) is a promising antibody partner for anti-human epidermal growth factor receptor 2 (HER2). We performed neoadjuvant chemotherapy (NAC) for HER2-positive breast cancer (BC) using nab-PTX plus trastuzumab (T-mab) and pertuzumab (P-mab), followed by epirubicin and cyclophosphamide (EC). Methods In this multicenter phase II clinical trial (January 2019–July 2020), patients with stage I (T1c)-IIIB HER2-positive primary BC were treated with four cycles of nab-PTX plus T-mab and P-mab, followed by four cycles of EC. The primary endpoint was the pathological complete response (pCR) rate. Secondary endpoints were clinical response rate (RR), adverse events (AE), and tumor-infiltrating lymphocytes (TILs) in biopsy samples. Results In total, 43 patients were enrolled (mean age, 54 years). Twenty-two patients had HER2, and 21 patients had luminal/HER2-subtypes. The overall pCR rate was 53.5% (23/43, 95% CI: 42.6–64.1%, p = 0.184), whilst the pCR for HER2 was 68.2% (15/22, 95% CI: 45.1–86.1) and 38.1% for luminal/HER2 (8/21, 95% CI: 18.1–61.6%). The RR was 100% [clinical (c) CR:25, partial response (PR): 18]. AEs (≥ G3) included neutropenia (23.3%), leukopenia (7.0%), liver dysfunction (7.0%), and peripheral neuropathy (4.7%) when nab-PTX was administered. EC administration resulted in leukopenia (34.2%), neutropenia (31.6%), and febrile neutropenia (15.8%). The TILs in preoperative biopsy samples were significantly higher in pCR compared to non-pCR samples. Conclusion Nab-PTX plus T-mab and P-mab induced a high pCR rate in HER2-positive BC, particularly in the HER2-subtype. Given that AEs are acceptable, this regimen is safe and acceptable as NAC for HER2-positive BC.