Safety and effectiveness of eribulin in Japanese patients with locally advanced or metastatic breast cancer: a post-marketing observational study

Background This large-scale study was conducted to evaluate the safety and effectiveness of eribulin for the treatment of inoperable or recurrent breast cancer in real-world settings in Japan. Methods Between July and December 2011, eligible patients with inoperable or recurrent breast cancer receiving eribulin for the first time were centrally registered and observed for 1 year. Eribulin was administered intravenously (1.4 mg/m²) on days 1 and 8 of every 3-week cycle. The primary endpoint was the frequency and intensity of adverse drug reactions (ADRs). Secondary endpoints included overall response rate (ORR) and time to treatment failure (TTF). Results Of 968 patients registered at 325 institutions, 951 and 671 were included in the safety and effectiveness analyses, respectively. In the safety population, ADRs were observed in 841 patients (88.4%). The most common (≥15% incidence) were neutropenia (66.6%), leukopenia (62.4%), lymphopenia (18.4%), and peripheral neuropathy (16.8%). The most common grade ≥ 3 ADRs (>5% incidence) were neutropenia (59.8%), leukopenia (50.5%), lymphopenia (16.1%), and febrile neutropenia (7.7%). In the effectiveness population, ORR was 16.5% (95% confidence interval: 13.7, 19.4). The median TTF was 127 days (95% confidence interval: 120, 134). Conclusions The safety and effectiveness profile of eribulin was consistent with prior studies. Eribulin had a favorable risk-benefit balance when used in real-world clinical settings.