Phase 2, Multicenter, Single-Arm Study of Eribulin Mesylate With Trastuzumab as First-Line Therapy for Locally Recurrent or Metastatic HER2-Positive Breast Cancer

In this multicenter, phase II, single-arm study, 52 patients with recurrent or metastatic HER2-positive (+) breast cancer received first-line eribulin with trastuzumab. The objective response rate (ORR) was 71.2% (n = 37) with a median time to first response (TTR) of 1.3 months; duration of response (DOR) and progression-free survival (PFS) were 11.1 and 11.6 months, respectively. Eribulin/trastuzumab combination resulted in a substantial tumor response with an acceptable safety profile. Background: The aim of this study was to assess efficacy and safety of eribulin with trastuzumab as first-line therapy for locally recurrent or metastatic HER2+ breast cancer. Patients and Methods: In this multicenter, phase II, single-arm study, patients with recurrent or metastatic HER2+ breast cancer received eribulin mesylate at 1.4 mg/m(2) intravenously (I.V.) on days 1 and 8 of each 21-day cycle with an initial trastuzumab dose of 8 mg/kg I.V. on day 1, followed by 6 mg/kg of trastuzumab on day 1 of each subsequent cycle. Tumor assessments were conducted every 6 weeks for the first 6 cycles and every 12 weeks thereafter. The primary end point was ORR, and secondary end points included PFS, TTR, DOR, and safety. Results: Fifty-two patients were enrolled. Fifty-one patients (98.1%) had metastatic disease, 25 (48.1%) with liver metastases, 24 (46.2%) with lung metastases, and 19 (36.5%) with bone metastases. Patients received a median of 10.0 cycles of eribulin and 11.0 cycles of trastuzumab. The ORR was 71.2% (n = 37) with median TTR of 1.3 months, DOR of 11.1 months, and PFS of 11.6 months. The most common Grade 3/4 treatment-emergent adverse events were neutropenia in 20 (38.5%) patients, peripheral neuropathy in 14 (26.9%; all Grade 3) patients, fatigue in 4 (7.7%) patients, and febrile neutropenia in 4 (7.7%) patients. Conclusions: Because of the high ORR, prolonged median PFS, and acceptable safety profile, combination eribulin/trastuzumab is an acceptable treatment option for locally recurrent or metastatic HER2+ breast cancer.