Myocarditis Following Pembrolizumab Plus Axitinib, and Belzutifan Plus Lenvatinib for Renal Cell Carcinoma: A Case Report

Cardiac toxicity is an adverse event of several classes of anti-cancer drugs. Herein, we present the case of a 52-year-old woman with metastatic renal cell carcinoma (RCC), previously treated with debulking surgery, pembrolizumab (immune checkpoint inhibitor) in combination with axitinib (tyrosine kinase inhibitor (TKI)), followed by lenvatinib (TKI) and belzutifan (HIF-2α inhibitor), who developed myocarditis proven by cardiac magnetic resonance and endomyocardial biopsy. The case was notable for reporting a not-yet described adverse event during treatment with belzutifan plus lenvatinib, the etiology of which was of unobvious determination given the pre-exposure to pembrolizumab, a known cause of drug-related myocarditis. We surmise that myocarditis was a delayed adverse event related to pembrolizumab (8 months after treatment interruption), although we emphasize that only attentive monitoring of cardiac adverse events of patients exposed to belzutifan and lenvatinib in the context of large clinical trials may rule out any causal implication of these drugs.