This is an open-label, randomized, explorative phase II trial of lapatinib plus trastuzumab or lapatinib plus capecitabine in patients with HER2 overexpressing metastatic breast cancer. The trial is designed to obtain some evidence wether chemotherapy-free combined HER2-directed therapy with lapatinib and trastuzumab provides a similar efficacy as the established combination of lapatinib with capecitabine and a more favourable toxicity profile. This study will also assess the relationship between the anticipated anti-tumour activity of the treatment regimens and biological characteristics of subjects' tumour at baseline.~The purpose of this study is to estimate the clinical benefit of lapatinib plus trastuzumab compared to lapatinib plus capecitabine as measured by investigator-assessed progression-free survival, tumour response and overall survival.~The purpose of this study ist further~to characterize the safety and tolerability of lapatinib plus trastuzumab in this population.~to identify predictors of sensitivity to lapatinib and trastuzumab therapy. and~to compare the differences in health-related quality of life (HRQL) and pain symptoms for patients by treatment assignment.
The purpose of this study is to estimate the clinical benefit of lapatinib plus trastuzumab compared to lapatinib plus capecitabine as measured by investigator-assessed progression-free survival, tumour response and overall survival.