A Study of Limited Heart Monitoring During Non-anthracycline Trastuzumab-based Therapy in Breast Cancer Patients

Inclusion Criteria: * Age \>/= 18 years * Newly diagnosed histologically confirmed primary invasive breast carcinoma (Stage I-IV) * Pathologically confirmed HER2-positive breast cancer * Planned to receive trastuzumab-based therapy for a minimum of 12 months, or started trastuzumab-based therapy within the last weeks with a planned duration of at least 12 months. * Normal LV systolic function (EF greater than or equal to the institutional lower limit of normal) * William and able to comply with the requirements of the protocol Exclusion Criteria: * Planned to receive an anthracycline-based regimen * Prior history of treatment with anthracycline chemotherapy * History of cardiovascular including cardiomyopathy, heart failure, or any other clinically significant cardiovascular disease (as determined by the investigator) * Uncontrolled hypertension, defined as systolic blood pressure \>/= 160 mmHg and/or diastolic blood pressure \>/= 90 mmHg (as determined by the investigator)