In a cohort of 81 women with human epidermal growth factor receptor 2–positive breast cancer who were treated with anthracyclines followed by trastuzumab, 26 patients (32%) developed cardiotoxicity, as defined by the Cardiac Review and Evaluation Committee,35 and ultrasensitive troponin I, measured following completion of anthracycline use, predicted the development of cardiotoxicity.52 This evidence concerns the gene ERBB2 and breast cancer.