Effectiveness and safety of eribulin in Japanese patients with HER2-negative, advanced breast cancer: a 2-year post-marketing observational study in a real-world setting.

Background Data on eribulin as the first- or second-line treatment in a clinical setting, especially the overall survival (OS) of patients, are scarce. Therefore, we assessed the effectiveness and safety of eribulin as the first-, second-, and third- or later-line treatments in patients with human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer in Japan. Methods This multicenter, prospective, post-marketing, observational study enrolled patients from September 2014 to February 2016 in Japan and followed them for 2 years. Patients were categorized by eribulin use into the first-, second-, and third- or later-line treatment groups. Results Of 651 registered patients, 637 patients were included in the safety and effectiveness analysis. In all, first-, second-, and third or later-line treatment groups, median OS (95% confidence interval) were 15.6 (13.8-17.6), 22.8 (17.3-31.0), 16.3 (12.4-19.9), and 12.6 (11.2-15.1) months and time to treatment failure (TTF) (95% confidence interval) were 4.2 (3.7-4.4), 5.2 (3.7-5.9), 4.2 (3.7-5.1), and 3.8 (3.5-4.2) months, respectively. Prolonged TTF was associated with complications of diabetes and the development of peripheral neuropathy after eribulin treatment, according to multivariate Cox regression analysis. Grade ≥ 3 adverse drug reactions (ADRs) were reported in 61.7% of the patients. Neutropenia (49.5%) was the most common grade ≥ 3 ADR in all groups. Conclusions The effectiveness and safety results of eribulin as the first- or second-line treatment were favorable. Thus, these suggest eribulin may be a first-line treatment candidate for patients with HER2-negative advanced breast cancer in Japan.