Fatal Myocarditis Following Adjuvant Immunotherapy: A Case Report and Literature Review

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy by enhancing the immune response against tumors. However, they can cause immune-related adverse events (irAEs), including rare but potentially fatal myocarditis. We describe a 71-year-old man with stage IIIA lung adenocarcinoma treated with adjuvant pembrolizumab who developed severe ICI-associated myocarditis. Despite early diagnosis, treatment with intensive immunosuppression and mechanical support, he suffered fatal cardiac complications. A systematic review of the literature up to May 2025 identified 44 cases of ICI-associated myocarditis. Data on clinical features, diagnostics, treatment, and outcomes were extracted and analyzed. Most cases involved older patients with lung cancer treated with pembrolizumab or nivolumab. Onset varied from days to years after therapy initiation. Presentations included dyspnea, chest pain, arrhythmias, and elevated cardiac biomarkers. The biopsy showed T-cell and macrophage infiltration. High-dose corticosteroids were the primary treatment; additional immunosuppressants were used in cases that were refractory. Mortality was 45%, mainly due to cardiac failure and sepsis. Discussion: ICI-associated myocarditis arises from immune dysregulation affecting cardiac tissue, potentially involving shared antigens and systemic inflammation. Early detection and aggressive immunosuppression are crucial but often insufficient, resulting in high mortality. This underscores the urgent need for a better understanding of pathogenesis and the development of effective management strategies to improve patient outcomes. Finally, a multidisciplinary approach is important to improve outcomes in ICI-associated myocarditis.