Prospective screening for myocarditis in cancer patients treated with immune checkpoint inhibitors

BACKGROUND: Immune checkpoint inhibitors (ICIs) improve clinical outcomes in various cancers, but sometimes induce autoimmune adverse effects, including myocarditis, which is the most serious complication. There are many reports on ICI-induced myocarditis; however, only a few prospective surveillance reports exist. Therefore, we developed a prospective screening protocol and performed monitoring clinically suspected myocarditis in every patient treated with ICIs. METHODS: We prospectively enrolled 126 consecutive patients treated with ICIs in this cohort. Outcomes of patients were determined and analyzed between April 2017 and May 2020. We evaluated vital signs, biomarkers, electrocardiograms, chest radiographs, and echocardiographs before and at 7 ± 3, 14 ± 3, 21 ± 3, and 60 ± 7 days after ICI initiation. RESULTS: Eighteen (14.3 %) presented troponin I elevation and 13 of them presented signs of clinically suspected myocarditis (10.3 %). Among the 13 patients, ICI was discontinued in four cases (3.2 %) without fatal events. Myocarditis appeared at an early stage of ICI treatment, regardless of severity (median, 44 days). CONCLUSIONS: We observed the frequency of patients with myocarditis or myocardial damage through a prospective screening program in the real world. Although the frequency was higher than expected, most cases were mild and ICI treatment could be continued under careful observation.