Safety and activity of docetaxel and trastuzumab in HER2 overexpressing metastatic breast cancer: a pilot phase II study

We conducted a pilot phase II trial of trastuzumab administered concurrently with docetaxel in women with HER2-overexpressing advanced breast cancer. Twenty-five women with HER2-positive (3+ by immunohistochemistry = 16, 2+ = 9) metastatic breast cancer received docetaxel (75 mg/m every 3 weeks for 6 cycles) and trastuzumab (4 mg/kg loading dose, 2 mg/kg weekly thereafter). Twenty-three patients (92%) had visceral metastatic involvement. Twenty-three patients had received prior chemotherapy as part of adjuvant (18), metastatic (2), and both (3) treatment. The number of cycles administered was 121 (median 6, range 1-6). Symptomatic cardiotoxicity (GIII) occurred in one patient. The most common grade GIII/IV toxicity was neutropenia (80% of the cycles), although febrile neutropenia did not occur. No other GIII/IV toxicities were observed. Response rate was 70% (1 complete response and 15 partial responses) in 23 evaluable patients. The combination of docetaxel and trastuzumab is well tolerated and has clinically meaningful antitumor activity.