Defining the clinical utility of PET or PET-CT in idiopathic inflammatory myopathies: A systematic literature review

Abstract

ObjectivesPositron emission tomography (PET), often combined with computed tomography (CT), is a well-established tool for diagnosing malignancy and inflammatory disease. The idiopathic inflammatory myopathies (IIM) are chronic, multi-system diseases characterised by skeletal muscle inflammation, the potential for extramuscular manifestations such as interstitial lung disease (ILD) and an increased risk of malignancy. We performed a systematic literature review to evaluate the utility of PET or PET-CT in evaluation of IIM. MethodsA search of Medline and EMBASE from 1990 to 2022 using keywords related to IIM and PET was performed. English language studies of adults with IIM who had PET or PET-CT were included. ResultsOur search identified 1173 potentially relevant abstracts, 19 of which were included. The majority of studies used [18F] fluorodeoxyglucose (FDG) PET or PET-CT scans, while the remainder used [18F] florbetapir and [11C] Pittsburgh compound B ([11C] PIB). The sensitivity and specificity of 18F-FDG-PET or 18F-FDG-PET-CT for diagnosing malignancy compared with standard detection methods was 66.7–94% and 80–97.8%, respectively. The sensitivity of 18F-FDG PET-CT for ILD was 93–100% when high-resolution CT was used as the reference standard. 18F-PET and 18F-FDG-PET-CT appear to accurately detect muscle inflammation, although correlations with clinical measures of IIM disease activity were variable. [18F] florbetapir PET-CT and [11C] PIB PET were able to differentiate sporadic inclusion body myositis (IBM) from non-IBM IIM. ConclusionPET-CT holds promise as a single tool that can simultaneously evaluate multiple aspects of IIM. These include screening for associated malignancy, achieving an early diagnosis of ILD and evaluating muscle inflammation.