Phase II Study of Weekly Docetaxel and Trastuzumab for Patients With HER-2–Overexpressing Metastatic Breast Cancer

Abstract

PURPOSE: To evaluate the safety and efficacy of weekly docetaxel plus trastuzumab in women with HER-2–overexpressing metastatic breast cancer. Efficacy was correlated with serum HER-2 extracellular domain (ECD) levels. PATIENTS AND METHODS: Thirty women with metastatic breast cancer were treated with weekly docetaxel and trastuzumab as first- or second-line therapy. Both docetaxel 35 mg/m2/wk and trastuzumab 2 mg/kg/wk were delivered in 4-week cycles consisting of three weekly treatments followed by 1 week of rest. A loading dose of trastuzumab 4 mg/kg was administered 1 day before the start of the first cycle. RESULTS: The median delivered dose-intensity of docetaxel was 24 mg/m2/wk (range, 18 to 27 mg/m2/wk). The intent-to-treat overall response rate (ORR) was 63% (95% confidence interval [CI], 44% to 80%). The ORR in patients whose tumors were HER-2–positive by fluorescence in situ hybridization was 67% (16 of 24 patients; 95% CI, 45% to 84%). In patients with elevated serum HER-2 ECD at baseline, the ORR was 76% (95% CI, 53% to 92%), compared with 33% (95% CI, 7% to 70%) in patients with low HER-2 ECD levels (P = .04). Variations in HER-2 ECD concentrations during treatment correlated with response to treatment. Median time to progression was 9 months. Acute toxicity, including myelosuppression, was mild. Fatigue, fluid retention, and excessive tearing became more common with repetitive dosing. CONCLUSION: Weekly docetaxel and trastuzumab is an active combination for treating patients with HER-2–overexpressing metastatic breast cancer. Serum HER-2 ECD testing may be a promising method for monitoring patients on trastuzumab-based therapy.