Abstract
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Objectives The aim of this study was to assess the role of serial FDG PET imaging for treatment response monitoring in patients with cardiac and extra-cardiac sarcoidosis by using metabolic and volumetric PET/CT indices.
Methods The study included 82 PET/CT scans of 20 subjects with both cardiac and extra-cardiac sarcoidosis who underwent serial FDG PET imaging for treatment monitoring.In addition to qualitative assessment, all PET/CT scans were quantified by measuring SUVmax, SUVmean, metabolic active volume (MAV) and total lesion glycolysis (TLG=MAV*SUVmean) of cardiac and extracardiac lesions. Clinical response was determined by subjective symptom change and New York Heart Association (NYHA) classification.The relative changes of PET indices between baseline and follow-up scans were compared with clinical findings. Sensitivity and specificity of different FDG-PET indices for prediction of disease progression were calculated by receiver operation characteristics curve analyses.
Results PET finding was positive in 73 scans. Extra-cardiac involvement was found at lymph nodes (n=43) , lung (n=18), spleen (n=14) and bone marrow in 4 scans. Thirteen scans with inactive cardiac sarcoidosis had active extra-cardiac lesions, where the most common positive tissue was mediastinal lymph node. The changes of cardiac volumetric FDG PET indices showed robust correlations with clinical response. Relative changes of MAV, TLG, average SUVmax and SUVmean showed a good correlation with clinical response. For prediction of disease progression, relative changes of MAV of > 5.6 % offered 80% sensitivity and 85.71% specificity. Relative changes of TLG of > 17% gave 70% sensitivity and 85.71% specificity. The changes of extra-cardiac PET parameters were not robustly associated with clinical response.
Conclusions Quantitative FDG PET analysis has value in treatment response monitoring of sarcoidosis. Metabolic active volume and total lesion glycolysis changes showed promise as possible imaging biomarkers to evaluate disease progression.