Efficacy of docetaxel 60 mg/m2 in patients with metastatic breast cancer according to the status of anthracycline resistance.

PURPOSE: To evaluate the efficacy of docetaxel 60 mg/m2 in metastatic breast cancer (MBC) according to the status of anthracycline resistance. PATIENTS AND METHODS: Ninety-nine patients with anthracycline-resistant MBC were treated with docetaxel 60 mg/m2 intravenously for a 90-minute period every 3 to 4 weeks. Anthracycline resistance was defined as primary and secondary resistance. Primary resistance was defined as progression during or within 6 months after completion of adjuvant anthracycline, and no MBC response to a first-line regimen that contained anthracycline. Secondary resistance was defined as progression after a documented clinical response to a first-line anthracycline treatment for MBC. Secondary resistance was further divided into three categories: (1) absolute resistance, or progression during treatment with anthracycline after a period of response; (2) relative resistance, or progression within 6 months after anthracycline administration ended; and (3) sensitive regrowth, or progression more than 6 months after the conclusion of anthracycline administration. RESULTS: The response rate in the 99 patients was 35.4% (95% confidence interval, 30.1% to 44.8%). The response rates according to the status of anthracycline resistance were as follows: primary resistance (n = 46), 19.6%; secondary resistance (n = 53), 49.1% (absolute resistance [n = 16], 56.3%); relative resistance (n = 17), 47.1%; and sensitive regrowth (n = 20), 45.0%. The median time to treatment failure in patients with primary resistance was 2.9 months, compared with 5.2 months in patients with secondary resistance (P = .0022). CONCLUSION: Docetaxel at a dose of 60 mg/m2 seemed to be effective in MBC with secondary resistance to anthracycline. The status of anthracycline resistance is important for the prediction of response to second-line treatment with docetaxel.