Improved outcomes with early immunosuppression in patients with immune-checkpoint inhibitor induced myasthenia gravis, myocarditis and myositis: a case series.

PURPOSE: Myasthenia gravis (MG) is a rare but life-threatening complication of immune-checkpoint inhibitor (ICI) therapy and often co-presents with myositis and myocarditis. Previous case series of ICI-related MG have reported high mortality rates. We present a series of ten patients from a tertiary oncology centre outlining outcomes of an early multi-modal immunosuppression strategy. METHODS: We reviewed The Christie Hospital database of immunotherapy-related toxicity from 2017 to 2020. Symptom severity was assessed using the Myasthenia Gravis Foundation of America (MGFA) classification. RESULTS: Ten patients with ICI-related MG were identified. All patients presented following 1 (n = 4) or 2 (n = 6) cycles of ICI. Symptom progression was rapid with a median of 3 days from onset of symptoms to admission. Concomitant myositis and myocarditis were observed in nine patients. AChR or MuSK autoantibodies were positive in six patients. All patients received urgent treatment with intravenous methylprednisolone (IVMP) and eight received intravenous immunoglobulin (IVIG). A single patient died from myasthenia-related symptoms; the remaining 9 patients were successfully discharged. CONCLUSION: In our cohort, we demonstrate good outcomes associated with early intensive immunosuppressive treatment with IVIG and IVMP. An agreed national treatment protocol or clinical discussion forum would be beneficial.