Severe neuromuscular immune-related adverse events of immune checkpoint inhibitors at national cancer center in Korea

PURPOSE: Neuromuscular immune-related adverse events (irAEs) associated with immune checkpoint inhibitors (ICIs) have been increasingly recognized as a consequence of expanding use of ICIs in advanced cancers. We aimed to evaluate the frequency, phenotypes, rescue treatment, and clinical outcomes of severe neuromuscular irAEs of ICIs at National Cancer Center (NCC), Korea. MATERIALS AND METHODS: Consecutive patients with newly developed severe neuromuscular irAEs (common terminology criteria for adverse events grade 3 or greater) after ICI treatment at NCC in Korea between December 2018 and April 2022 were included by searching neuromuscular diagnostic codes in electronic medical records and/or reviewing neurological consultation documentations. RESULTS: Of the 1,503 ICI-treated patients, nine (0.6%) experienced severe neuromuscular irAEs; five with pembrolizumab and four with atezolizumab. The patients included five women and four men; their median age at onset was 59 years. The irAEs included Guillain–Barre syndrome (n = 5) and myasthenia gravis (MG) crisis with myositis (n = 4), and developed after a median of one (range 1–5) ICI cycle. The median modified Rankin score (mRS) was 4 (range 3–5) at the nadir. ICIs were discontinued in all patients, and rescue immunotherapy included corticosteroids (n = 9), intravenous immunoglobulin (n = 7), and plasmapheresis (n = 2). Eight patients showed improvements, with a median mRS of 3 (range 1–4); however, one patient (who had MG crisis with myocarditis) died. CONCLUSIONS: In this real-world monocentric study, ICI-induced neuromuscular irAEs were rare but potentially devastating; thus, physicians should remain vigilant to enable prompt recognition and management of irAEs.