Gemcitabine and trastuzumab in metastatic breast cancer.

The background, rationale, and preliminary results of a phase II trial of gemcitabine plus trastuzumab in heavily pretreated metastatic breast cancer patients are presented. Gemcitabine and trastuzumab both exhibit single-agent activity in previously treated metastatic breast cancer. Preclinical studies of gemcitabine and trastuzumab in combination showed additive or synergistic antitumor effects in human breast cancer cell lines that overexpress HER2. A multicenter phase II trial was thus conducted to define the safety and efficacy of gemcitabine/trastuzumab in patients previously treated for metastatic breast cancer. Women with measurable metastatic breast cancer whose primary or secondary tumor overexpressed HER2 were eligible for inclusion. Gemcitabine 1,200 mg/m(2) was administered on days 1 and 8 of a 21-day cycle. Trastuzumab was administered at a loading dose of 4 mg/kg initially, then at 2 mg/kg weekly thereafter. Preliminary analysis of 38 evaluable patients showed that gemcitabine/trastuzumab was well tolerated and had significant antitumor activity in this patient population. The study is now concluded, and final analysis of the data is nearing completion. Publication of the results is anticipated in 2003.