134P Safety and efficacy of eribulin and trastuzumab in anti-HER2 therapy pretreated patients with HER2-positive metastatic breast cancer: A Japanese multicenter phase 2 study (SBP-04 study)

Abstract

Background: The efficacy of eribulin for HER2 negative metastatic breast cancer (MBC) was confirmed by EMBRACE trial. However, there is no definitive Asian evidence about efficacy and safety of eribulin combined with trastuzumab (ET) for HER2 positive MBC. Methods: This study is a prospective multicenter phase II trial. HER2 positive MBC patients pretreated by chemotherapy with anti-HER2 drugs were enrolled. They received eribulin (1.4mg/m2) on day1 and 8 of each 21 days and trastuzumab by weekly (2mg/kg) or tri-weekly (6mg/kg) until progressive disease. Primary endpoint is objective response rate (ORR). Secondary endpoints are progression free survival (PFS), overall survival (OS), and safety. Results: 25 patients were enrolled. Median age was 62 (range 32-79). ER and PgR expression were positive in 15 (60%) and 9 (24%) patients approximately. Metastatic sites were 3 (12%) Bone/soft tissue and 22 (88%) visceral. 4 patients diagnosed brain metastases. The number of pretreated chemotherapy regimens was median 3 (range 2-7). 20 (80%) MBC patients had received taxane. Median cycle of ET was 5 (range 1-42). ORR and CRR were 36% and 48%. Best responses were CR: 1 (4%), PR: 8 (32%), SD: 7 (28%) and PD: 8 (36%). Long SD (> 6 months) was 3 (12%). Median PFS and OS were 5 and 30 months. Grade 3 adverse events were peripheral sensory neuropathy (12%), fatigue and appetite loss (4%), neutropenia (52%), leukopenia (36%) and ALT increased (4%). Conclusions: This study demonstrated that the combination therapy of eribulin and trastuzumab is effective and well-tolerated regimen for pretreated HER2 positive MBC patients, and appears to make disease stable for long time period.