Outcomes of Immune Check Point Inhibitor Use in US Veterans With Pre-Existing Idiopathic Inflammatory Myopathies: Case Series and Literature Review.

OBJECTIVE: Our objective was to identify and describe the clinical characteristics and outcomes in patients with pre-existing idiopathic inflammatory myopathies (IIMs) in the Veterans Health Administration (VHA) treated with immune checkpoint inhibitors (ICIs). METHODS: All veterans receiving ICI infusions were identified. Patients with at least two International Classification of Disease codes for IIM before first ICI infusion underwent chart review to identify patients with confirmed IIM by American College of Rheumatology/EULAR criteria. The demographics, cancer diagnoses, laboratory findings, clinical course, and mortality rates were reported. IIM cases were also reviewed to determine if patients developed IIM flare following ICI treatment. RESULTS: We identified 29,539 veterans who received at least one ICI infusion in the VHA between June 6, 2011, and February 14, 2023. The eight patients with confirmed IIM before ICI treatment were mostly White men with an average age of 71.7 years at first ICI infusion. The IIM diagnoses were dermatomyositis in three patients, polymyositis in two, antisynthetase syndrome in two, and one rheumatoid arthritis (RA)/myositis overlap. Cancer diagnoses were lung (two), melanoma (two), head and neck (two), kidney/other urinary (one), and mesothelioma (one). Diagnosis of IIM was made on average 3.1 years before ICI treatment. One patient had an IIM flare after ICI. No IIM flares were identified in other patients. CONCLUSION: Our findings show that an IIM flare after ICI therapy can occur, but most patients did not develop a flare. These observations suggest ICIs can be considered as an option in patients with cancer with IIM with shared decision-making and close monitoring.