Heart Failure With Reduced Ejection Fraction Caused by Osimertinib in a Patient With Lung Cancer: A Case Report and Literature Review.

Osimertinib is widely used for the treatment of advanced lung cancers harboring  () mutations. Because of its inhibitory activity on the human epidermal growth factor receptor 2 pathway, osimertinib-induced cardiotoxicity is concerning. Large-scale international clinical studies revealed a subclinical decline in the left ventricular ejection fraction (LVEF) with osimertinib, which allowed a continuation of the drug. Only a few studies have reported symptomatic heart failure with reduced ejection fraction (HFrEF) with osimertinib, and its clinical impact in real-world settings remains unclear. A 91-year-old man was diagnosed with lung adenocarcinoma harboring an mutation and was started on osimertinib. The treatment conferred substantial tumor regression; however, the patient presented with symptomatic HFrEF six weeks after osimertinib initiation. Transthoracic echocardiography demonstrated diffuse hypokinesis of the left ventricular walls with a significantly reduced ejection fraction from the baseline. Initial evaluation showed no causative cause of heart failure, and we suspected osimertinib-associated cardiomyopathy. Discontinuation of the drug along with the cardioprotective approach improved cardiac symptoms and restored the LVEF to baseline within a week. Here, we comprehensively review the literature and discuss the clinical features of HFrEF following osimertinib administration. Physicians should be aware of rare complications associated with osimertinib therapy.