Abstract 14733: Major Adverse Cardiac Events and the Timing and Dose of Corticosteroids in Immune Checkpoint Inhibitor-Associated Myocarditis

IntroductionMyocarditis is a potentially fatal complication of immune checkpoint inhibitors (ICI). While corticosteroids are the cornerstones of the treatment, there are no data to guide the dose and timing.MethodsFrom an international registry of patients with ICI myocarditis diagnosed between 2013 and 2019, data on the type, dose (in methylprednisolone equivalent dose) and timing of steroids were extracted. Major cardiovascular events (MACE) were a composite of cardiovascular death, cardiogenic shock, cardiac arrest, and hemodynamically-significant complete heart block.ResultsIn total, 143 ICI myocarditis patients (67±13 years old, 29% women) were included. Among them, 125 received corticosteroids (87%), with the initial agent being either methylprednisolone (95, 76%), prednisone (25, 20%), hydrocortisone (2, 1.6%) or dexamethasone (3, 2.4%). The rates of overall MACE (by admission time tertile 145.8%, tertile 243.8%, tertile 338.3%, P=0.746) and individual elements of MACE were unchanged from 2013 to 2019. The initial corticosteroid dose was categorized as low (500mg). There was an inverse relationship between the occurrence of MACE and initial dose of corticosteroid, where MACE declined with increasing doses (low 61.9%, intermediate 54.6%, high 20.4%, P72 hours (85.7%, P