Detection of muscle involvement and extramuscular lesions using 18F-FDG PET/CT in patients with PM/DM

1688 Objectives Clinician often seek sensitive and specific imaging techniques to detect myositis and extramuscular lesions in patients withinflammatory myopathy. The aim of this study was to assess the utility of 18F-FDG PET/CT in the management of patients with polymyositis (PM) / dermatomyositis (DM). Methods 12 untreated PM/DM patients (3 PM and 9 DM; 5 women and 7 men; age range 13-78 years, mean age 53±20 years) who underwent 18F-FDG PET/CT were reviewed retrospectively between April 2010 and December 2014. The diagnosis of PM/DM was based on the criteria by Bohan and Peter. All images were interpreted independently by two experienced nuclear medicine physicians without knowledge of patients’ history. Final diagnosis was made by consensus of two readers. FDG uptake into muscles was judged positive when the intensity of muscles was higher than the background. The maximum standardized uptake value (SUVmax) was calculated for muscles and extramuscular lesions. Results FDG uptake into proximal muscles was detected in all patients (100%), the mean of SUVmax was 2.9±1.0 (range 1.8-4.9). FDG PET/CT detected neoplasms in 6 patients with associated malignancy (4 lung cancer, 2 nasopharyngeal carcinoma), the median of SUVmax was 6.2 (range 4.4-16.2). Moreover, FDG uptake in lungs was found in 4 of 5 patients with interstitial lung disease (ILD). Conclusions 18F-FDG PET/CT is a potent tool for the diagnosis and its additional benefits in malignancy screening and ILD assessment in patients with PM/DM.