Abstract
BACKGROUND: Combination chemotherapy has improved cancer outcomes; however, identifying suspected cardiotoxic chemotherapies can be challenging when multiple chemotherapies are initiated simultaneously. CASE SUMMARY: 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. DISCUSSION: 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. TAKE-HOME MESSAGE: Multidisciplinary discussions are crucial for identifying suspected cardiotoxic chemotherapy and exploring additional chemotherapy options, including rechallenging immune checkpoint inhibitors.