1014 Background: Treatment with trastuzumab and chemotherapy has improved the outcome of HER2-positive MBC. It is unknown what the outcome and toxicity is of monotherapy trastuzumab, followed by chemotherapy at progression, as compared to the combination of chemotherapy/trastuzumab. Methods: HER2-positive MBC pts., being eligible for first line chemotherapy were randomised between combination treatment docetaxel (TAX) (100 mg/m2, q3wks)/trastuzumab (HER) (loading dose 4mg/kg, whereafter weekly 2mg/kg) (arm A) or monotherapy HER, followed upon progression by TAX (similar doses as arm A) (arm B). Further in- /exclusion criteria were adjuvant non-taxoid chemotherapy allowed, previous HER treatment not; normal ejection fraction (EF), adequate liver/renal functions and bone marrow reserve. Primary endpoint was PFS, secondary endpoints: response rate (RR), overall survival (OS) and toxicities. Kaplan-Meier curve was tested by log-rank test, RR by Pearson χ2-test. Results: Of the 101 randomly selected patients, ...