Troponin I Surveillance to Risk-Stratify Early Events After Immune Checkpoint Inhibitor Initiation.

Background: Troponin surveillance may facilitate early detection of immune checkpoint inhibitor (ICI)-associated myocarditis, but mild elevations and baseline abnormalities complicate interpretation. We assessed early post-ICI troponin I (TnI) dynamics and the performance characteristics of clinically applicable peak TnI thresholds within 3 months of ICI initiation. Methods and Results: We analyzed 281 participants from a cardio-oncology surveillance program. TnI was measured at predefined intervals. Using peak TnI levels within 3 months, we evaluated the performance characteristics of candidate TnI thresholds for identifying adjudicated clinically significant TnI elevation associated with clinically meaningful conditions (e.g., ICI-associated myocarditis) at cut-offs of 50, 100, and 500 pg/mL. Eleven (3.9%) patients had elevated baseline TnI. Within 3 months, clinically significant TnI elevation occurred in 5 (1.8%) patients: ICI-associated myocarditis (n=2); immune-related myositis (n=1); pulmonary embolism (n=1); and seizures (n=1). A 50 pg/mL cut-off yielded 100% sensitivity, 96.0% specificity, 31.3% positive predictive value, and 100% negative predictive value. A 100 pg/mL cut-off demonstrated 100% sensitivity, 99.6% specificity, 83.3% positive predictive value, and 100% negative predictive value. A 500 pg/mL cut-off yielded 40.0% sensitivity and 100% specificity. Conclusions: In this exploratory study, a peak TnI threshold of 100 pg/mL within 3 months identified all clinically significant events with high specificity. This threshold may serve as a pragmatic trigger for expedited evaluation of myocarditis and alternative etiologies.