Following the pivotal clinical trials of trastuzumab (Herceptin), further phase II and III studies have been initiated. Preliminary results from a phase II, dose-response study of single-agent trastuzumab in 113 HER2-positive metastatic breast cancer patients without prior chemotherapy for stage IV disease have shown that the overall response rate was 23% (six complete responses and 20 partial responses), with similar results using both standard- and high-dose regimens of trastuzumab. Another phase II study of trastuzumab plus paclitaxel, both given weekly, in 63 HER2-positive and -negative patients with metastatic breast cancer produced an overall response rate of 62% in HER2-positive and 44% in HER2-negative patients. A further phase II study is underway to investigate the combination of trastuzumab plus docetaxel in 30 HER2-positive patients with metastatic breast cancer. Finally, a number of European studies are at an advanced stage of planning or are about to start patient recruitment. These include docetaxel +/- trastuzumab, aromatase inhibitor +/- trastuzumab, CMF (cyclophosphamide, methotrexate, 5-fluorouracil) +/- trastuzumab, vinorelbine + trastuzumab, all in HER2-positive patients, and epirubicin-cyclophosphamide (EC) + trastuzumab in HER2-positive patients vs. EC alone in HER2-negative patients. The results from these trials should be available over the next one to two years.
