Major Adverse Cardiovascular Events and the Timing and Dose of Corticosteroids in Immune Checkpoint Inhibitor–Associated Myocarditis

Introduction: myocarditis 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.\n\nMethods: from 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.\n\nResults: in 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 1: 45.8%, tertile 2: 43.8%, tertile 3: 38.3%, P=0.746) and individual elements of MACE were unchanged from 2013 to 2019. The initial corticosteroid dose was categorized as low (<60mg), intermediate (≥60mg and ≤500mg) and high (>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%, P<0.001). The median time from admission to the first corticosteroids was 45 (15.5, 89) hours. Patients receiving corticosteroids within 24 hours had significantly lower MACE (7.0%) compared to those between 24-72 hours (34.3%) and those >72 hours (85.7%, P<0.001). The dose interacted with timing of initiation whereby high dose corticosteroids within 24 hours achieved the best outcome and low corticosteroids after 72 hours had the worst outcome (Fig 1).\n\nConclusions: ICI myocarditis is associated with high rate of MACE. Higher initial dose and earlier initiation of corticosteroids were associated with improved outcomes.