Left Ventricular Dysfunction Caused by Combined Pembrolizumab and Lenvatinib Following Doxorubicin

Combination chemotherapy has improved cancer outcomes; however, identifying suspected cardiotoxic chemotherapies can be challenging when multiple chemotherapies are initiated simultaneously. A 58-year-old woman with endometrial cancer developed heart failure, with a reduced left ventricular ejection fraction of 26%, 10 months after combined pembrolizumab and lenvatinib after doxorubicin. Cardiac magnetic resonance revealed acute myocarditis. Endomyocardial biopsy revealed interstitial fibrosis and scattered CD3-positive T-lymphocyte infiltration without myocytic necrosis. After discontinuation of pembrolizumab and lenvatinib, left ventricular function recovered without steroids. Pembrolizumab monotherapy was resumed for lung metastasis. This case highlights the importance of identifying different cardiotoxic mechanisms. Potential causes of left ventricular dysfunction could overlap with immune checkpoint inhibitor-induced myocarditis from pembrolizumab and reversible cardiotoxicity from lenvatinib, based on myocardial fibrosis caused by doxorubicin cardiotoxicity. Multidisciplinary discussions are crucial for identifying suspected cardiotoxic chemotherapy and exploring additional chemotherapy options, including rechallenging immune checkpoint inhibitors.