Efficacy and safety of ixabepilone in taxane-resistant patients with metastatic breast cancer previously treated with anthracyclines: results of a phase II study in Japan

Anthracycline and taxane resistance is a key issue in the treatment of metastatic breast cancer (MBC), particularly in Asian patients who often present with advanced disease. The objective of this study was to investigate the efficacy and safety of ixabepilone monotherapy in Japanese patients with taxane-resistant MBC previously treated with anthracycline. Japanese patients with taxane-resistant MBC previously treated with anthracycline were treated with 40 mg/m(2) ixabepilone every 3 weeks. Primary endpoint was overall response rate. Secondary endpoints included duration of response, time to progression (TTP), and safety. Fifty-two patients were treated with ixabepilone. Overall response rate was 11.5 % (95 % confidence interval 4.4-23.4), stable disease rate was 38.5 %, duration of response was 3.6 months (range 2.4-5.3 months), and TTP was 2.8 months (range 0.7-8.1 months). The most frequent grade 3/4 toxicities were neutropenia (82.7 %), leukopenia (75 %), myalgia (19.2 %), and peripheral neuropathy (19.2 %). Ixabepilone monotherapy was effective and toxicities were manageable in this phase II study of Japanese patients with taxane-resistant metastatic breast cancer previously treated with anthracyclines.