Abstract:
Objective To investigate whether 18F-FDG PET/CT can effectively assess muscle disease activity in inflammatory myopathy (IM) without malignant tumors.
Methods The clinical data and 18F-FDG PET/CT imaging data from 66 IM patients without malignant tumors were retrospectively collected. The maximum standardized uptake value (SUVmax) of a total of 16 bilateral muscles (deltoid, biceps brachii, triceps brachii, pectoralis major, psoas major, gluteal muscles, adductor group, and quadriceps) was measured in all patients. The mean value of these measurements was calculated as the muscle standardized uptake value (SUVM), which was then normalized using the liver SUV (SUVLIV) to obtain SUVM/SUVLIV. The Myositis Intention to Treat Activity Index (MITAX) was used to evaluate muscle disease activity, and patients were divided into active and inactive groups for intergroup comparison. The diagnostic performance of SUVM/SUVLIV in assessing disease activity in IM patients was analyzed using receiver operating characteristic (ROC) curve analysis. Spearman’s rank correlation was used to analyze the correlations between SUVM/SUVLIV and patients’ general characteristics, laboratory parameters, and other relevant variables.
Results The SUVM/SUVLIV in active patients was 0.66 (0.54, 0.95), significantly higher than that in inactive patients 0.48 (0.34, 0.52), with statistical significance (Z=3.952, P<0.001). ROC curve analysis showed that the optimal SUVM/SUVLIV cutoff value for distinguishing active from inactive groups was 0.57, with a sensitivity of 65.3%, specificity of 94.1%, and an area under the curve (AUC) of 0.824. Correlation analysis revealed that SUVM/SUVLIV was significantly associated with MITAX score (r=0.595, P<0.001), CK (r=0.590, P<0.001), CK-MB (r=0.420, P<0.001), ferritin (r=0.558, P<0.001), and CRP (r=0.355, P=0.005), but not significantly correlated with disease subtype (r=0.073, P=0.559).
Conclusion The semi-quantitative parameter SUVM/SUVLIV derived from 18F-FDG PET/CT holds potential value in the diagnosis and management of IM patients without malignant tumors. SUVM/SUVLIV can effectively assess muscle disease activity in IM patients without malignant tumors.