A phase II study on metastatic breast cancer patients treated with weekly vinorelbine with or without trastuzumab according to HER2 expression: changing the natural history of HER2-positive disease.

PURPOSE: To observe whether in pretreated metastatic breast cancer patients with HER2-positive disease vinorelbine plus trastuzumab can produce different overall response rate (ORR), time to progression (TTP), and overall survival (OS) from women with HER2-negative tumors treated with vinorelbine alone.
METHODS: Between June 2000 and January 2004, 68 consecutive women were enrolled: 33 patients received vinorelbine (V) alone, while 35 patients were given trastuzumab plus vinorelbine (T+V) according to HER2 expression determined by immunohistochemistry. In tumors scored +2, HER2 gene amplification was determined by fluorescence in situ hybridization.
RESULTS: In patients treated with V (HER2-negative tumors) the ORR was 27.3%, while in those given T+V (HER2 positive tumors) the ORR was 51.4%. The median duration of response was 8 months for women treated with V and 10 months for those who received T+V. Patients given T+V had a longer TTP (9 months) and OS (27 months) than those receiving V alone (6 months and 22 months respectively). Toxicity was mild in both groups. Concerning cardiotoxicity in T+V group, 7 patients (20%) had left ventricular systolic disfunction.
CONCLUSION: Our data suggest that trastuzumab can change the natural history of HER2-positive metastatic breast cancer. In fact, when treated with trastuzumab, women with HER2-positive disease had better prognosis than patients with HER2-negative tumors. Conducting a formal phase III trial comparing vinorelbine alone vs vinorelbine plus trastuzumab in HER2-positive metastatic breast cancer women could be debatable.