Statement: in order to qualify for the primary clinical trial, one must possess an ecog score fewer than 2
Primary_evidence: 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