The fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection in Chinese patients with HER2-positive early breast cancer: primary analysis of the phase III, randomized FDChina study

Abstract Background Neoadjuvant fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection (PH FDC SC) demonstrated non-inferior cycle 7 pertuzumab and trastuzumab serum trough concentrations (C trough ), and similar total pathological complete response (tpCR) rates and safety, to intravenous pertuzumab plus trastuzumab (P + H IV) in HER2-positive early breast cancer (eBC). In the FDChina study (NCT04024462), we assessed neoadjuvant–adjuvant PH FDC SC vs. P + H IV in Chinese patients with HER2-positive eBC. Methods Patients received four doxorubicin (60 mg/m 2 ) plus cyclophosphamide (600 mg/m 2 ), then four docetaxel (75–100 mg/m 2 ) cycles, every 3 weeks. Patients were randomized 1:1 to PH FDC SC (loading: 1200 mg pertuzumab/600 mg trastuzumab; maintenance: 600 mg/600 mg) or P + H IV (loading: 840 mg/8 mg/kg; maintenance: 420 mg/6 mg/kg) alongside docetaxel before surgery. Patients then continued HER2-targeted therapy for 14 cycles. Co-primary non-inferiority endpoints: cycle 7 pertuzumab and trastuzumab C trough . Secondary endpoints: tpCR, long-term efficacy, safety. Results The lower bounds of the 90% confidence intervals of pertuzumab and trastuzumab cycle 7 geometric mean ratios (0.99 and 1.44, respectively) exceeded the pre-specified non-inferiority margin (0.8). tpCR rates were 55.6% for PH FDC SC vs. 56.4% for P + H IV. Grade ≥ 3 adverse events occurred in 72% vs. 69% of patients. Conclusion The study met the co-primary endpoints of non-inferiority of cycle 7 serum C trough for pertuzumab and trastuzumab for PH FDC SC vs. P + H IV. tpCR rates and safety were comparable between arms. PH FDC SC may be a viable treatment option for Chinese patients with HER2-positive eBC.