Phase 1 Dose-Escalation Study of Triweekly Nab-Paclitaxel Combined With S-1 for HER2-Negative Metastatic Breast Cancer

A phase 1 dose-escalation study of low-dose triweekly nab-paclitaxel for metastatic breast cancer was performed. The recommended dose was 220 mg/m(2) nab-paclitaxel with 80 mg/m(2) S-1. The toxicity was tolerable, and the response rate and the disease control rate were 60.0% and 70.0%, respectively. This regimen was feasible and safe with sufficient efficacy, and could be tolerated as a late-line therapy. Purpose: To evaluate the efficacy, toxicity, maximum tolerated dose, and recommended dose of triweekly nab-paclitaxel (nab-PTX) and S-1 combination chemotherapy for patients with metastatic breast cancer. Patients and Methods: This phase 1 study was conducted with a standard 3 3 dose escalation design. Every 3 weeks, the patients received nab-PTX at 180-260 mg/m(2) on day 1 and S-1 at 65-80 mg/m(2) daily on days 1 to 14. Results: Ten HER2-negative metastatic breast cancer patients were enrolled; their median number of prior chemotherapy regimens was 3. Dose-limiting toxicity was observed in the first patient assigned to level 4; grade 4 febrile neutropenia and grade 3 neurotoxicity such as needing a wheelchair occurred. Therefore, an additional patient was not assigned to level 4. The maximum tolerated dose was considered level 4 (260 mg/m 2 nab-PTX with 80 mg/m(2) S-1). The recommended dose determined was level 3 (220 mg/m(2) nab-PTX with 80 mg/m(2) S-1). The response rate was 60.0%. The disease control rate was 70.0%. Conclusion: This combination chemotherapy therapy was feasible and safe for patients with HER2-negative metastatic breast cancer. (C) 2020 Elsevier Inc. All rights reserved.