- Histologically confirmed diagnosis of breast cancer.
- Presence of metastatic disease.
- Documentation of HER2 gene amplification or overexpression.
- Available tumor tissue for central review of HER2 status.
- At least 1 measurable lesion as defined by RECIST 1.1.
- Eastern Cooperative Oncology Group status of 0 to 2.
- Left ventricular ejection fraction within institutional range of normal, measured by
either two dimensional echocardiogram or multigated acquisition scan.
- Relapse within 1 year of last dose of previous adjuvant (including neoadjuvant)
treatment (except endocrine therapy) and within 1 year before randomization.
- Prior systemic therapy for metastatic disease (except endocrine therapy).
- Prior cumulative dose of doxorubicin of >400 mg/m2, epirubicin dose >800 mg/m^2, or
the equivalent dose for other anthracyclines or derivatives (eg, 72 mg/m^2 of
mitoxantrone). If the patient has received more than one anthracycline, then the
cumulative dose must not exceed the equivalent of 400 mg/m^2 of doxorubicin.
- Inflammatory breast cancer.
- Active uncontrolled or symptomatic central nervous system metastases.