Safety and efficacy study of oral metronomic vinorelbine combined with trastuzumab (mNH) in HER2-positive metastatic breast cancer: a phase II trial

Purpose We conducted a single-arm prospective phase II trial to evaluate the efficacy and safety of oral metronomic vinorelbine combined with trastuzumab (mNH) in human epidermal growth factor receptor 2-positive (HER2-positive) metastatic breast cancer (MBC) patients. Methods HER2-positive MBC patients received oral vinorelbine 40 mg thrice a week and trastuzumab (loading dose of 8 mg/kg, followed by 6 mg/kg every 3 weeks) until disease progression, unacceptable toxicity, or consent withdrawal. The primary endpoints were objective response rate (ORR), clinical benefit rate (CBR; CR + PR + SD for ≥ 24 weeks). The secondary endpoints were progression-free survival (PFS), tolerability, and overall survival (OS). Results Twenty patients with HER2-positive MBC were enrolled, with a median of 1 prior chemotherapy regimens for MBC. Median age was 61.5 years (95% Confidence Interval (CI) 48.6–63.1). Visceral involvements presented in 14 patients (70.0%). ORR was 20.0%, and CBR was 75% with 4 PR (20.0%) and 11 SD (55.0%). The median PFS (mPFS) and median OS (mOS) were 7.4 months (95% CI 3.2–11.5) and 45.8 months (95%CI: not reached), respectively. The mPFS was 17.7 months (95%CI not reached) and 5.8 months (95%CI 5.6–5.9) in mNH as first-line and ≥ second-line therapy (log rank p = 0.03), respectively. The most common grade 1 adverse events (AEs) included nausea (15%), leukopenia (15%), ALT/AST elevation (15%), diarrhea (10%), and peripheral neuropathy (10%). Grade 2 adverse events included leukopenia (5%) and neutropenia (10%). No grade 3/4 AEs were observed. Conclusions Oral metronomic vinorelbine combined with trastuzumab is a well-tolerated and effective anti-tumor regimen for HER2-positive MBC.