Lapatinib+Vinorelbine vs Vinorelbine HER2 Positive Metastatic Breast Cancer Progressed After Lapatinib/Trastuzumab

This study is a multicenter, randomized, open label, phase II study. Patients will be randomized to either lapatinib plus vinorelbine (LV) arm or vinorelbine alone (V) arm, if they are satisfied by inclusion and exclusion criteria. The stratification factors are followings: 1) visceral metastasis vs. others, 2) previous response to lapatinib treatment, complete response(CR)+partial response(PR) vs. stable disease(SD)≥ 12wks. Patients in LV arm will receive daily lapatinib 1,000mg with vinorelbine 20mg/m2 day1 and day 8. Patients in V arm will receive vinorelbine 30mg/m2 day 1 and day 8. Treatment repeats every 21 days unless there is any evidence of disease progression or unacceptable toxicity or noncompliance by patient with protocol requirements. Response will be documented by physical examination, chest or abdomen CT prior to treatment as a baseline, and every 2 cycles (window period ± 1 week) after a start of treatment and at 18 weeks.