Abstract / Summary
Abstract Background Immune checkpoint inhibitors improve outcomes in several cancers but can cause immune-related adverse events. ICI-associated myocarditis is uncommon and potentially fatal. This review summarizes evidence on its incidence, features, morbidity, mortality, and management in adults with cancer. Main Body We searched PubMed, EMBASE, Scopus, Web of Science, and the Cochrane Library to January 2026 (PROSPERO CRD42024547168; PRISMA). Ten observational studies were included. Four studies (11,164 ICI-exposed patients) gave a pooled incidence of 1.93% (95% CI 1.42–2.63; prediction interval 1.39–2.68). Three studies (191 myocarditis cases) gave a pooled short-term/as-reported mortality of 22.1% (95% CI 6.8–52.5; prediction interval 4.3–64.4). The wide interval reflects few studies and non-uniform follow-up. Overlap events, especially myositis, were often described. High-dose corticosteroids were the main treatment. Diagnostic criteria varied. Conclusion ICI-associated myocarditis is uncommon but can be fatal. Mortality estimates are imprecise. Severity and overlap syndromes are potential prognostic features from individual studies, not a pooled analysis. Standardized criteria and prospective cohorts are needed.