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.