Real-world clinical effectiveness of eribulin in metastatic breast cancer patients with visceral metastases in the United States.

e13058 Background: Eribulin mesylate was approved in the United States (US) in 2010 for the treatment of metastatic breast cancer (mBC) after at least two prior chemotherapeutic regimens, which should have included an anthracycline and a taxane in either the adjuvant or metastatic setting. Visceral metastases, including those to the lung and brain, have been identified as poor prognostic features for patients with mBC. The objective of this analysis was to assess the real-world clinical effectiveness of eribulin in mBC patients with visceral metastases when treated in accordance with the US label. Methods: Patients with mBC initiating eribulin consistent with the US label between 2011-2017 were identified through a retrospective, multi-site chart review study conducted in US oncology practices. De-identified, patient-level demographics, clinical characteristics, treatment patterns, and outcomes were entered into an electronic case report form by the patients’ treating physicians. Sites of metastases at initiation of eribulin were indicated by providers. Clinical outcomes assessed included best overall response to eribulin as recorded in the patient’s chart, progression-free survival (PFS), and overall survival (OS). The proportion of patients with either a complete or partial response as their best overall response was calculated. PFS and OS were calculated by the Kaplan-Meier method from the initiation of eribulin for all patients with visceral metastases and subsets reporting lung or brain metastases site, respectively. Results: The analysis included 470 patients with visceral metastases, including 342 with lung metastases and 22 with brain metastases at the time of eribulin initiation. Eribulin was third-line therapy for approximately three quarters of patients in these subgroups, and the remainder received eribulin in fourth line or later. Mean age was 59 years in general (59 and 54 years in those with lung and brain metastases, respectively). Over half of patients (53.6%) had either a complete or partial response to eribulin. Median PFS was estimated at 6.0 months, and median OS was estimated at 10.5 months. Results for the subgroups of patients with lung and brain metastases are shown in the table. Conclusions: The results of this retrospective analysis affirm clinical effectiveness of eribulin in mBC patients with visceral metastases, when used consistent with the US label.[Table: see text]