Abstract P6-17-28: Outcomes of real-world use of eribulin plus trastuzumab for HER2-positive metastatic breast cancer
Authors: Mougalian SS , Copher R , McAllister L , Radtchenko J , Wang EC , Broscious M , Yu H-T , Kish J 
Published: May 2019

Abstract
Background
Eribulin mesylate is approved for the treatment of metastatic breast cancer (mBC) after two prior chemotherapy regimens including an anthracycline or a taxane in either the metastatic or adjuvant setting. Eribulin in combination with trastuzumab (E+T) has demonstrated tolerability and anti-tumor activity in phase I and II trials but is not FDA-approved for the treatment of HER2-positive mBC. Case series and retrospective research have noted the use of E+T in clinical practice. We sought to describe patient characteristics and long-term outcomes of treatment with E+T for HER2-positive mBC patients treated outside of clinical trials in the US.
Methods
US-based community oncologists from an open network of over 7,000 oncologists, hematologists, and urologists were invited to participate in identifying HER2-positive mBC patients treated with E+T between 01/01/11 and 12/31/13 outside of clinical trials. Data were collected from 03/18/2016 until 09/01/2016. Providers completed an electronic case report form (CRF) by abstracting data on disease characteristics, treatment patterns, disease response (per provider assessment), adverse events (Aes), and date of death. Duration of treatment and overall survival (OS) were calculated from the initiation of the E+T regimen. The target sample size was 60 patients and patients were selected according to resource available for chart data abstraction.
Results
Twenty-three providers submitted CRFs for 62 total patients. After data collection, 59 of 62 submitted records were validated for analysis. At mBC diagnosis, 69.4% of patients were ER/PR negative and 42.4% of patient had de novo stage IV disease. At initiation of E+T, the median age was 57 years and 81.4% were ECOG-OS 0/1. Mean length of follow-up from the initiation of any therapy was 33.6 months. Twenty-two (37.3%) patients initiated E+T as their first- or second-line of treatment; those remaining were in third-line or greater. At initiation of E+T, 72.8% of patients had prior treatment with trastuzumab in combination with chemotherapy, 25.4% had prior trastuzumab in combination with pertuzumab and chemotherapy, and 16.9% had received TDM-1. Mean duration of E+T treatment was 5.2 months (SD=2.4). A response (complete [CR] or partial [PR]) was recorded by the providers for 64.4% of patients (not independently verified). The most common Aes reported were fatigue (67.8%), weakness (50.8%), decreased appetite (28.8%), decreased hemoglobin (27.1%), peripheral neuropathy (25.4%), and neutropenia (18.6%). At the end of the study period, 34 patients (57.6%) were deceased; the median OS from the initiation of E+T was 23.9 months (95% CI: 17.8-30.4).
Conclusions
In a small cohort of patients treated with E+T in the community setting, the observed response rate of 64.4% (CR+PR) was comparable to that of a prior phase II trial of E+T which reported an ORR with first-line E+T of 71.2% overall, 77.4% among T-naïve and 61.9% in T-pretreated patients. Further research is warranted to examine the tolerability and efficacy of E+T for metastatic HER2-positive breast cancer patients in different treatment settings.
Citation Format: Mougalian SS, Copher R, McAllister L, Radtchenko J, Wang EC, Broscious M, Yu H-T, Kish J. Outcomes of real-world use of eribulin plus trastuzumab for HER2-positive metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-28.