A prospective study of 136 HER2+ breast cancer patients showed patients experiencing trastuzumab-induced cardiotoxicity had lower baseline LVEF (n = 6, LVEF 57.08 ± 1.36%) compared to the control (n = 125, LVEF 61.42 ± 0.26%) in response to trastuzumab treatment [122]. This evidence concerns the gene ERBB2 and breast cancer.