Efficacy and safety of eribulin in Japanese patients (pts) with advanced breast cancer.

Abstract

1081 Background: Eribulin mesylate (E7389) is a nontaxane microtubule dynamics inhibitor with a novel mechanism of action currently in development for the treatment of advanced breast cancer and other solid tumors. This study evaluated the efficacy and safety of eribulin in Japanese pts with advanced breast cancer. Methods: This was a single-arm, open-label phase 2 study in pts with metastatic breast cancer (MBC) or locally advanced disease (RECIST measurable disease), ECOG performance status 0-2, previously treated with an anthracycline and a taxane. Pts had received ≤3 prior chemotherapy (CT) regimens in the metastatic setting, and either progressed within 6 months of their last CT or relapsed within 12 months of adjuvant or neoadjuvant CT. Eribulin mesylate (1.4 mg/m2) was administered as a 2-5 minute intravenous (IV) infusion on days 1 and 8 of a 21-day cycle. The primary efficacy endpoint was objective response rate (ORR; number of pts with complete response [CR] or partial response [PR] divided by the number of pts in the analysis population) as assessed by independent review (IR) using RECIST criteria. Results: Of the 84 pts enrolled, 81 received eribulin and had the following characteristics: median age 54 (range: 31-72) yrs; ER-positive or PgR- positive (65%); HER2/neu-positive (11.3%); triple ER, PgR, HER2-negative (27.5%). The median of number of prior CT regimens was 3. The median number of treatment cycles with eribulin was 5 (range 1-20). ORR was 21.3% (CR 0, PR 17 pts; 95% CI 12.9, 31.8%). SD was 37.5% and the clinical benefit rate (CR + PR + SD>6 months) was 27.5% (95% CI 18.1, 38.6%). The median duration of response was 119.0 days (95% CI 85.0, 148.0 days). Median progression-free survival (PFS) was 112.0 days (95% CI 61.0, 133.0 days) and median overall survival (OS) was 331.0 days (95% CI 234.0, - days [upper CI not determined due to shortage of events]). Six-month PFS and OS rates were 20.1% and 72.3%, respectively. The most frequent treatment-related grade 3/4 toxicities were neutropenia (95.1%), leukopenia (74.1%), febrile neutropenia 13.6%, and lymphopenia (12.3%). Grade 3 peripheral neuropathy occurred in 3.7% of pts (no grade 4). Conclusions: Eribulin was effective and tolerable treatment for heavily pretreated pts with MBC or locally advanced disease. No significant financial relationships to disclose.