First-line bevacizumab in combination with weekly paclitaxel for metastatic breast cancer: efficacy and safety results from a large, open-label, single-arm Japanese study

Despite extensive evaluation of first-line bevacizumab-containing therapy in randomized trials in locally recurrent/metastatic breast cancer (LR/mBC), data from Japanese populations are limited. We conducted a phase II study exclusively in Japanese patients to evaluate bevacizumab combined with weekly paclitaxel. Patients with HER2-negative measurable LR/mBC who had received no prior chemotherapy for LR/mBC received bevacizumab 10 mg/kg, days 1 and 15, in combination with paclitaxel 90 mg/m², days 1, 8, and 15, repeated every 4 weeks, until disease progression, unacceptable toxicity, or patient/physician decision. Co-primary endpoints of this single-arm open-label phase II study were progression-free survival (PFS) and safety. A total of 120 patients (median age 55 years) received study therapy. At the time of data cut-off, the median duration of therapy was 11.1 months (range 0.5–24.7 months). Median PFS was 12.9 months (95% CI: 11.1–18.2) according to Independent Review Committee assessment and 14.9 months by investigator assessment. Median PFS was 9.6 months in the subgroup of 38 patients with triple-negative LR/mBC. The overall response rate was 74% (95% CI: 64.5–81.2%). Median overall survival (OS) was 35.8 months (95% CI: 26.4—not estimated) and the 1-year OS rate was 88.9% (95% CI: 83.2–94.6). The regimen was well tolerated and the safety profile was generally consistent with previous reports of bevacizumab–paclitaxel combination therapy. Grade 3 hypertension was reported in 17% of patients. Grade 4 hypertension, grade 3/4 proteinuria, and gastrointestinal perforation were absent. There were no new bevacizumab safety signals. In 50 patients (42%), treatment was continued for ≥1 year. Conclusion: The high activity of first-line bevacizumab in combination with weekly paclitaxel observed in our study confirms the results of the E2100 trial. Our results suggest that the activity and tolerability of first-line bevacizumab-containing regimens demonstrated in E2100 can be reproduced in Japanese populations.