In a select cohort of women with ERBB2 + breast cancer receiving sequential therapy with anthracyclines and trastuzumab, the objectives of our pilot study were to (i) assess whether macro-cTn is detectable early after therapy initiation, specifically post-anthracycline (~ 2 months after therapy initiation) and 3-months into trastuzumab therapy (~ 5 months after therapy initiation), and to (ii) explore whether there is an association between the presence of macro-cTn and changes in left ventricular ejection fraction (LVEF) or global longitudinal strain (GLS). This evidence concerns the gene ERBB2 and breast cancer.