Cardiotoxicity Alerts during Treatment with Trastuzumab in Breast Cancer at Four-year Follow-up

Background: Adjuvant treatment of HER2+ breast cancer includes adriamycin and trastuzumab, a monoclonal antibody that producescardiotoxicity. The actual epidemiologic impact of trastuzumab-related cardiotoxicity in unselected populations in Argentinaremains unknown.Objectives: The aim of this study was to evaluate the impact of trastuzumab-related cardiotoxicity during adjuvant treatment forbreast cancer in an unselected population after >12 months of completing therapy.Methods: Among 888 patients prospectively evaluated for breast cancer, 231 (38%) were HER2+ and received adjuvant therapy withadriamycin and trastuzumab. Left ventricular ejection fraction was evaluated before treatment, after completing adriamycin and thenevery 3 months during follow-up. Cardiotoxicity was defined as a decline in left ventricular ejection fraction >10%, according to the definitionof the American College of Cardiology and was compared with the definitions of the B-31 trial and the MD Anderson Cancer Center.Results: A decline in left ventricular ejection fraction >10% from baseline values occurred in 65% (n=150) of the patients during amean follow-up of 48±12 months. In the per group analysis, patients included in the B-31and MD Anderson Cancer Center vs. theAmerican College of Cardiology definitions presented greater percent fall in left ventricular ejection fraction during treatment: 20%vs. 20% vs. 16%, respectively (p <0.04) and ended treatment with left ventricular ejection fraction <50% in 42% vs. 41% vs. 33% ofcases, respectively (p=0.01).Conclusions: In the population treated with trastuzumab under cardio-oncology surveillance during 48±12 months:1- Left ventricular ejection fraction was significantly decreased in more than 60% of patients.2- Different guidelines show different cardiotoxicity risks which demands continuous cardio-oncological monitoring.