As an exploratory effort to identify putative modifying variants, we conducted a genetic association study of decline in LVEF following treatment with combination doxorubicin (known to induce cardiomyopathy in animal models and humans) and trastuzumab (a targeted therapy for ERBB2, crucial in prevention of dilated cardiomyopathy in mice [7] and known cardiotoxicity in clinical trials [10,15]) in 800 patients from a breast cancer clinical trial across 72 genes that are causative of cardiomyopathies. Here, ERBB2 is linked to breast carcinoma.