Consecutive patients with a first diagnosis of breast cancer will be identified at the Tom Baker Cancer Centre (TBCC) and included into the study, if they are going to receive chemotherapy with anthracyclines and / or Trastuzumab and do not have contra-indications for the CMR study. Besides the usual clinical care for these patients (e.g. blood samples before each cycle of chemotherapy; MUGA scans to follow cardiac size and function), the patients will undergo serial contrast-enhanced CMR studies (before, during and 9-12 months after completion of the chemotherapy); patients will be seen at an outpatient clinic in the Dept. of Cardiac Sciences / Heart Function Clinic for a clinical assessment (including ECG, additional blood test like Troponin-T, BNP, 6-minute-walk-test) and recommendations will be made to medical treatment in patients with evidence for heart failure.