ICI-related myocarditis diagnosed in 1.1% of over 11,000 ICI-treated patients.

ICIrM diagnoses peaked in 2023–2024, reflecting increased clinical awareness.

The diagnostic rate rose after the release of Bonaca and ESC-ICOS guidelines.

No seasonal trend in ICIrM incidence was observed across the cohort.

Findings support enhanced vigilance and guideline-based early detection.

Immune checkpoint inhibitors (ICIs) have transformed cancer treatment, yet their use carries the risk of ICI-related myocarditis (ICIrM), a rare but potentially fatal adverse event. Although the overall incidence of ICIrM has been described, recent trends and diagnostic shifts remain poorly characterized.

We retrospectively reviewed 11,602 patients treated with ICIs at a multi-center institution from 2011 to 2024. ICIrM cases were identified through manual chart review, and baseline characteristics, cardiovascular events, and outcomes were assessed. The study was designed as a descriptive analysis of temporal trends in ICI therapy use and ICIrM.

ICIrM occurred in 127 patients (1.1%), with a mean age of 66.7 ± 12.7 years and 56.5% male. Median time to onset was 45 days (IQR 106). ICI use increased steadily over the past decade, with a marked rise in ICIrM diagnoses in 2023–2024, accounting for 47.2% of all cases. Diagnostic prevalence rose from 0.5% before 2020 to 1.3% after 2020, likely reflecting enhanced recognition due to the implementation of guideline-based diagnostic criteria (Bonaca et al. and ESC-ICOS). Seasonal variation in ICIrM incidence was not observed.

The increasing incidence of ICIrM likely reflects improved clinical awareness and diagnostic practices. Continued efforts to optimize surveillance, early detection, and mitigation strategies are essential as ICI use expands globally.

Immune-checkpoint inhibitor

ICI-related myocarditis

Cardiotoxicity

Diagnostic trends

© 2026 The Authors. Published by Elsevier B.V.