Asymptomatic and symptomatic cardiac toxicity associated with immune checkpoint inhibitors: insights from a Japanese registry.

Aims: Immune checkpoint inhibitors (ICIs) are a cornerstone of cancer therapy; however, immune-related adverse events, including myocarditis, pose significant challenges. Furthermore, limited data exist on the pathology of mild or asymptomatic cases. This study aimed to characterize the clinical, biomarker, and pathological features of ICI-associated cardiac toxicity, comparing symptomatic and asymptomatic cases within a Japanese multicentre registry. Methods and results: A nationwide, retrospective registry collected data from 90 patients across 23 hospitals between 2020 and 2022. Patients were classified according to the American Society of Clinical Oncology Clinical Practice Guidelines: Grade 1 (asymptomatic) and Grades 2-4 (symptomatic). Endomyocardial biopsy was performed in 24 patients ( Conclusion: This study provides one of the largest pathological and biomarker-based comparisons of symptomatic and asymptomatic ICI-associated cardiac toxicity. Our findings suggest that asymptomatic cases may represent a distinct, less aggressive inflammatory phenotype, characterized by lower CD8+ infiltration and limited myocardial damage.