In conclusion, we present both detailed phenotypic characterization of cardiac function, including echocardiography and CPET, in breast cancer survivors with and without BRCA1/2 mutations treated with anthracyclines, and in vitro characterization using anthracycline-treated, wild type vs. gene-modified human iPSC-CMs with a loss of function mutation in BRCA1. Overall, we found no strong evidence to support associations between BRCA1/2 mutations and anthracycline-induced cardiac dysfunction based on echocardiography, CPET or in vitro data. The gene discussed is BRCA1; the disease is breast cancer.