116P Real-world treatment patterns and clinical effectiveness of eribulin in HR+/HER2- metastatic breast cancer patients in the United States

Eribulin mesylate was approved in the US in 2010 for metastatic breast cancer (mBC) following at least two chemotherapeutic regimens; prior therapy should include anthracycline and taxane in the adjuvant or metastatic setting. With the changing treatment landscape in HR+/HER2- mBC, the main objective of our analyses was to assess the real-world clinical effectiveness of eribulin in HR+/HER2- mBC, when prescribed consistent with the US label. A retrospective chart review study of mBC patients initiating eribulin per US label between 2011-2017 was conducted across US community oncology practices. De-identified data were extracted by prescribing physicians from patients’ medical records and captured via an electronic case report form. Clinical outcomes assessed included provider-reported best overall response (defined as complete + partial response), progression-free survival (PFS), and overall survival (OS) in the HR+/HER2- mBC patients overall and those treated with eribulin post cyclin-dependent kinase inhibitor (CDKi), respectively. A total of 233 mBC patients with HR+/HER2- subtype treated with eribulin met the study inclusion criteria: mean age was 61 years and 55% had an ECOG status of 0 or 1. Median duration of eribulin treatment was 5.8 months, with 67% treated in 3rd line and 33% in ≥4th line. Best overall response on eribulin was 52% and median PFS for eribulin was estimated at 6.1 months. Landmark OS at 12 and 24 months was 46% and 26%, respectively. Approximately 31% (n=72) of the HR+/HER2- mBC patients had received a CDKi prior to eribulin. In the post CDKi subgroup, median duration of eribulin treatment was 4.5 months, and 74% were treated in 4th line or later. Best overall response on eribulin was 40%. Median PFS for eribulin in the post CDKi subgroup was estimated to be 4.6 months. Landmark OS at 12 and 24 months in the post CDKi subgroup was 39% and 19%, respectively. Results of these retrospective analyses reinforce the clinical effectiveness of eribulin in HR+/HER2- mBC patients including those previously treated with a CDKi, when used in accordance with the eribulin US label in clinical practice.