LUX-Breast 1: BIBW 2992 (Afatinib) in HER2-positive Metastatic Breast Cancer Patients After One Prior Herceptin Treatment

Inclusion criteria: * Histologically confirmed diagnosis of HER2-overexpression breast cancer * Stage IV metastatic disease * Must have progressed on one prior trastuzumab treatment * no more than one prior trastuzumab based therapy regimen (either adjuvant or first-line) * Must have received anthracycline and/or taxane based chemotherapy for adjuvant treatment of breast cancer or first-line treatment of metastatic breast cancer * Must have (archived) tumour tissue sample available for central re-assessment of HER2-status * At least one measurable lesion according to RECIST 1.1. * Eastern Cooperative Oncology Group (ECOG) score of 0 or 1 . Exclusion criteria: * Prior treatment with Epidermal Growth Factor Receptor/Human Epidermal Growth Factor Receptor(EGFR/HER2)-targeted small molecules or antibodies other than trastuzumab * Prior treatment with vinorelbine * Known pre-existing interstitial lung disease * Active brain metastases * History or presence of clinically relevant cardiovascular abnormalities such as uncontrolled hypertension, congestive heart failure NYHA classification of 3, unstable angina or poorly controlled arrhythmia. Myocardial infarction within 6 months prior to randomisation. * Cardiac left ventricular function with resting ejection fraction of less than 50%. * Patients unable to comply with the protocol. * Any contraindications for therapy with vinorelbine or trastuzumab. * Known hypersensitivity to BIBW 2992 or the excipients of any of the trial drugs. * Use of any investigational drug within 4 weeks of randomisation. * Inadequate hepatic, renal and haematologic organ function