Abstract 16450: Increased Monocyte Count and Neutrophil-to-Lymphocyte Ratio With ICI Myocarditis

Abstract

Introduction: Diagnosing immune checkpoint inhibitor (ICI) myocarditis remains complex in practice, often requiring advanced imaging or invasive endomyocardial biopsy. We constructed an institutional cohort of patients who received at least 1 dose of ICI and developed probable or definite ICI myocarditis. Hypothesis: We hypothesized that routine serum biomarkers, including troponin I, neutrophil-to-lymphocyte ratio (NLR), monocytes, and AST/ALT, would be elevated and peak at diagnosis. Methods: This retrospective cohort study used EHR data from patients on ICI at a single academic institution who developed probable or definite myocarditis from 7/2015 - 1/2023. Inclusion criteria and diagnosis date were defined using Bonaca criteria and/or documented clinical consensus, e.g. initiation of steroids for presumed myocarditis. Primary outcomes were levels of troponin I/high sensitivity troponin I, monocytes, NLR, and AST/ALT. LOESS regression with default smoothing parameter α = 0.75 was used to evaluate biomarker patterns 7 days pre- and post- diagnosis. Results: We included 16 cases of myocarditis. At diagnosis, most patients had at least 1 significant elevation in troponin I (100%), AST (81%), ALT (63%), or monocytes (69%) while on ICI (Figure 1). After diagnosis, absolute monocyte and lymphocyte count initially decreased before rebounding. Serum NLR rose prior to and briefly after diagnosis (Figure 2). Conclusions: Peripheral cardiac and non-cardiac biomarkers change with ICI myocarditis. Further research on routine non-cardiac biomarkers associated with myocarditis and other ICI toxicities may help prevent high-grade adverse events.