Use of Cytotoxic Chemotherapy in Metastatic Breast Cancer: Putting Taxanes in Perspective

Agents that target microtubule (MT) dynamics have been used extensively for the treatment of metastatic breast cancer (MBC). Among these agents are taxanes (solvent-based paclitaxel [sb-paclitaxel], docetaxel, and nab-paclitaxel) and non-taxanes, such as eribulin and ixabepilone. Although these agents have been approved for the treatment of MBC, questions regarding the ideal agent, regimen (single agent vs. combination vs. sequential), and schedule still remain. This systematic review examined pivotal trials for taxanes, eribulin, and ixabepilone as well as first-line taxane trials in MBC. Only randomized trials that enrolled ≥ 100 patients were included. Publications on combination regimens with targeted agents were excluded unless they also included a comparison between nontargeted regimens. The studies were grouped into taxane versus taxane, sb-paclitaxel versus non-taxane, and docetaxel versus non-taxane regimens. In taxane versus taxane comparisons, the efficacy of sb-paclitaxel and docetaxel appeared similar, nab-paclitaxel every 3 weeks (q3w) appeared superior to sb-paclitaxel q3w, and weekly nab-paclitaxel appeared superior to docetaxel. In general, taxane regimens demonstrated higher overall response rates (ORRs) versus non-taxane regimens; however, only 2 trials demonstrated longer overall survival (OS) for taxane regimens. Taxanes will likely continue to be used in earlier lines of therapy, whereas eribulin and ixabepilone may be more appropriate for later lines of treatment. Ongoing research may identify biomarkers that could help in selecting the appropriate MT-targeted agent for a given patient.