Immune checkpoint inhibitor related myositis: an observational, retrospective, pharmacovigilance study.

BACKGROUND: Immune checkpoint inhibitors (ICIs) hold promise as treatment options for various types of cancer. However, recent case reports have brought attention to myositis, a potentially life-threatening complication associated with ICIs. This study aims to assess the spectrum of myositis associated with ICIs, including its clinical features, risk factors for fatal cases, adverse events (AEs) accompanying ICIs-related myositis, and the risk of myositis in different populations in real-world settings.

RESEARCH DESIGN AND METHODS: We conducted an observational, retrospective pharmacovigilance study using the Food and Drug Administration adverse event reporting system (FAERS) database, covering data from inception to quarter 3 of 2022. We employed the information component (IC) and reporting odds ratio (ROR) to evaluate the association between ICIs and myositis. Logistic regression analysis was performed to elucidate the factors related to fatal outcomes. All analyzes were conducted using R version 3.2.5.

RESULTS: A total of 558 cases were identified as ICIs-associated myositis. Our study revealed a significant association between ICIs and myositis (ROR 15.54 [14.23-16.96], IC 3.79 [3.66-3.92], Figure 1). Notably, myositis was reported more frequently in patients treated with ICI combination therapy compared to those receiving ICI monotherapy (ROR 1.72 [1.39-2.11], IC 0.63 [0.30-0.93]). The risk of ICI-associated myositis increased with age, and age was also identified as a risk factor for fatality in cases of ICIs-associated myositis ( p  = 0.011). The most common accompanying AE observed were myocarditis (21.33%), followed by severe myasthenia gravis (16.49%) and malignant neoplasm progression (8.06%). The proportion of fatal cases was significantly higher for myositis accompanied by myocarditis, severe myasthenia gravis, and malignant neoplasm progression compared to non-fatal cases.[Figure: see text].

CONCLUSIONS: Clinicians should be aware of the potential for ICI-associated myositis, as it can be particularly life-threatening, especially in elderly patients or when it occurs concurrently with other AEs such as myocarditis or severe myasthenia gravis.