A phase II study of docetaxel in patients with paclitaxel-resistant metastatic breast cancer.

PURPOSE: To evaluate the efficacy and safety of docetaxel in patients with paclitaxel-resistant metastatic breast cancer (MBC). PATIENTS AND METHODS: Docetaxel (100 mg/m2) was administered every 3 weeks to 46 patients registered at four centers. Patients had previously received < or = two chemotherapy regimens for MBC. All patients had progressive disease while receiving paclitaxel therapy. Treatment was repeated until there was evidence of disease progression or for a maximum of three cycles after best response. RESULTS: Objective responses were seen in eight of 44 assessable patients (18.1%; 95% confidence interval CI, 6.7% to 29.5%). Seven patients had partial responses and one patient responded completely. Response rates were not significantly different by previously received paclitaxel dose or resistance. No responses were seen in 12 patients who had previously received paclitaxel by 24-hour infusion, but the response rate in 32 patients who had received paclitaxel by 1- to 3-hour infusion was 25%. The median response duration was 29 weeks and the median time to disease progression was 10 weeks. Median survival was 10.5 months. Clinically significant (severe) adverse events included neutropenic fever (24% of patients), asthenia (22%), infection (13%), stomatitis (9%), neurosensory changes (7%), myalgia (7%), and diarrhea (7%). CONCLUSION: Docetaxel is active in patients with paclitaxel-resistant breast cancer, particularly in those who failed to respond to brief infusions of paclitaxel. Response rates were comparable to or better than those seen with other therapies for patients with paclitaxel-resistant MBC. This confirms preclinical studies, which indicated only partial cross-resistance between paclitaxel and docetaxel.