Whole-body FDG PET/CT for evaluating disease activity in patients withpolymyositis/dermatomyositis

Objectives: The purpose of this study was to investigate the usefulness of whole-body FDG PET/CT for evaluating disease activity in patients with polymyositis/dermatomyositis (PM/DM). Materials and Methods: A total of 48 patients with previously untreated PM/DM were examined with whole-body FDG PET/CT. The same number of age- and sex-matched control patients with non-muscular diseases were also identified. The FDG uptake was visually evaluated in 22 regions of the whole-body. Regions with FDG uptake greater than that of the mediastinum blood vessels were considered positive. The semi-quantitative analysis was also performed using a maximum standardized uptake value (SUVmax). PET findings were correlated with biochemical markers [creatine kinase (CK), aldolase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH)].

Results: On visual analysis, the mean ± SD of number of positive regions in patients with PM/DM was 12 ± 6. The mean ± SD value of SUVmax in patients with PM/DM (3.67 ± 1.78) was significantly higher than that in control patients (1.32 ± 0.20) (p<0.001). There was a significant correlation between SUVmax and number of positive regions (p<0.02). There was no significant correlation between SUVmax and any biochemical markers. The number of positive regions showed a significant correlation with aldolase (p<0.03), AST (p<0.03), ALT (p<0.02), and LDH (p<007).

Conclusions: These preliminary results suggest that whole-body FDG PET/CT, especially number of FDG positive regions, may be useful for evaluating disease activity in patients with PM/DM.