Patients
In this prospective observational study, 651 patients were registered from 182 institutions, and of these, 637 patients were included in the safety and effectiveness analysis.
The baseline characteristics of the patients are summarized in Table 1. In each treatment line, 142 (22.3%), 177 (27.8%), 151 (23.7%), 75 (11.8%), 57 (8.9%), and 34 (5.3%) patients used eribulin as first-, second-, third-, fourth-, and fifth or later-line treatment at baseline, respectively. The mean age (± standard deviation [SD]) of patients in each line was similar: 59.4 ± 11.5, 59.6 ± 10.7, and 59.6 ± 10.9 years in the first-, second-, and third or later-line treatment group, respectively. Baseline characteristics in each group did not largely differ, except for ECOG PS, which ranged from 0 to 3 in each of the three treatment groups: 69.0%–1.4%, 63.3%–0.6%, and 47.0%–0.6%, respectively.
Table 1 Baseline characteristics The proportions of patients who started eribulin at 1.4 mg/m2 were 79.1%, 88.0%, 79.1%, and 75.1% for all, first-, second-, and third or later-line treatment groups, respectively (Table 2).
Table 2 Eribulin treatment status Effectiveness of using OS
In the effectiveness analysis, 632 of 637 patients were included in the analysis of survival after treatment with eribulin after excluding 5 patients with unknown survival status. In all, first-, second-, and third or later-line treatment groups, the median OS (95% CI) 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, respectively (Table 3).
Table 3 Kaplan-Meier estimates for OS and TTF after the treatment with eribulin Overall, the 1- and 2-year survival rates were 58.2% and 35.9%, respectively (Table 3). In the first-, second-, and third or later-line treatment groups, the 1- vs. 2-year survival rates were 71.6% vs. 48.3%; 58.2% vs. 37.0%; and 52.0% vs. 29.5%, respectively (Table 3).
Effectiveness using TTF
Excluding 1 patient with an incalculable eribulin administration period, 636 of 637 patients were included in the analysis of TTF. In all, first-, second-, and third or later-line treatment groups, the median TTF (95% CI) 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 (Table 3).
Overall, 10.4% and 3.0% of the patients were estimated to have continued with the eribulin treatment for 1 year and 2 years, respectively (Table 3). In the first-, second-, and third or later-treatment-line, 14.1%, 11.9%, and 7.9% of the patients were estimated to have continued with the eribulin treatment, respectively (Table 3).
Factors affecting TTF according to multivariate cox regression
Multivariate Cox regression analysis was performed to identify the factors influencing TTF. The following factors were significantly associated with the reduced TTF: ≥1 ECOG PS, triple-negative, a history of radiotherapy, liver metastasis, complication of liver dysfunction, AST ≥32 IU/l at baseline, and hemoglobin <11.5 g/dl at baseline. The complication of diabetes and the development of peripheral neuropathy after eribulin treatment was associated with prolonged TTF (Fig. 1).
Safety
Overall, in the first-, second-, and third or later-line treatment groups; 83.2%, 86.6%, 82.5%, and 82.0% of the patients showed ADRs for all grades, respectively (Table 4).
Table 5 summarizes the results of those with grade ≥ 3 ADRs in all, first-, second-, and third or later-line treatment groups. Overall, 61.7% of the patients reported grade ≥ 3 ADRs. In all, first-, second-, and third or later-line treatment groups, the most commonly observed grade ≥ 3 ADRs were neutropenia (49.5%, 54.2%, 48.6%, and 47.6%, respectively); followed by leukopenia (36.6%, 36.6%, 31.6%, and 39.1%, respectively); and lymphopenia (11.8%, 10.6%, 9.6%, and 13.6%, respectively) (Table 5). Other grades ≥3 ADR incidences were below 5.5% in each group (Table 5).
Seventy (11.0%) patients discontinued eribulin treatment due to the ADRs. ADRs occurring in ≥1% of the patients that resulted in eribulin discontinuation were leukopenia (3.0%), neutropenia (2.8%), peripheral sensory neuropathy (2.4%), and malaise (1.3%).