en Oncology Oncology Letter to Editor Letter to Editor <span style="font-size:14px;"><span style="font-family:Times New Roman;">Trastuzumab is a cornerstone therapy in HER2-positive breast cancer, yet its association with cardiotoxicity remains a major limitation in clinical practice. Trastuzumab-induced cardiac dysfunction, although often considered non-necrotic and potentially reversible, frequently manifests as left ventricular ejection fraction decline and symptomatic heart failure, leading to treatment interruption and compromised oncologic outcomes (1, 2). These clinical challenges highlight the need for a proactive, mechanism-oriented strategy in managing trastuzumab-related cardiac adverse effects. </span></span> Levosimendan, HER2 signaling, Trastuzumab, Cardiotoxicity, Mitochondrial dysfunction 688 689 http://caspjim.com/browse.php?a_code=A-10-3583-3&slc_lang=en&sid=1 Zahra Nazari Taloki zahra_nazari_taloki@yahoo.com 100319475328460057983 100319475328460057983 Yes Cancer Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran