Eribulin, trastuzumab, and pertuzumab as first-line therapy for patients with HER2-positive metastatic breast cancer: a phase II, multicenter, collaborative, open-label, single-arm clinical trial.

Purpose To examine the efficacy and safety of triple therapy with eribulin, trastuzumab, and pertuzumab in patients with HER2-positive metastatic breast cancer (MBC) who never received any prior therapy in the first-line metastatic/advanced setting. Methods Eribulin 1.4 mg/m (days 1 and 8), trastuzumab 8 mg/kg over 90 min and 6 mg/kg over 30 min, and pertuzumab 840 mg/body over 60 min and 420 mg/body over 30 min were administered intravenously in 21-day cycles. Results 25 women (median age, 57 years [range, 41-75 years]) received a median of 10 cycles (range, 0-34 cycles); 24 had performance status (PS) 0, 1 PS 1, 8 stage IV breast cancer, and 17 recurrence. Lung and liver metastases occurred in 9 and 9 patients, respectively. Median time to treatment failure with eribulin was 9.1 months (95% confidence interval [CI], 4.3-13.9 months), and median progression-free survival was 23.1 months (95% CI, 14.4-31.8 months). The overall response rate (complete response [CR] + partial response [PR]) was 80.0% (95% CI, 59.3-93.2%), and the clinical benefit rate (CR + PR + stable disease ≥24 weeks) was 84.0% (95% CI, 63.9-95.5%). The most common treatment-emergent adverse events (TEAEs) were alopecia (92.0%), fatigue (68.0%), and sensory peripheral neuropathy (60.0%). Grade 3/4 TEAEs occurred in 11 patients (44.0%). The only grade 4 TEAE was neutrophil count decreased (16.0%). Neither grade 4 peripheral neuropathy nor febrile neutropenia occurred. Conclusions ETP therapy showed acceptable efficacy and safety and is a potential first-line therapy for patients with HER2-positive MBC.