Diagnostic Performance of ¹⁸F-FDG PET/CT Semiquantitative Analysis in the Management of Sarcoidosis

Background: Sarcoidosis is a multisystem granulomatous disorder of unknown origin characterized by nonspecific clinical symptomatology. 18F-FDG PET/CT can visualize activated inflammatory cells of sarcoidosis and simultaneously provide whole-body images. Objective: To evaluate the clinical usefulness of 18F-FDG PET/CT and its semiquantitative parameters for the assessment of treatment efficacy in patients with sarcoidosis. Methods: Thirty-one consecutive patients who performed 18F-FDG PET/CT for sarcoidosis assessment were selected. All subjects performed 18F-FDG PET/CT before any treatment (PET1) and after 6-12 months (PET2). SUVmax and SUVmean on PET1 and PET2 were collected. SUVs values were employed to evaluate the ratios with the liver (R-LIVERmax, R-LIVERmean) and the blood (R-BLOODmax, R-BLOODmean). The difference between the PET1 and PET2 values was evaluated (ΔSUVmax, ΔSUVmean, ΔR-LIVERmax, ΔR-LIVERmean, ΔR-BLOODmax, ΔR-BLOODmean). Patients were classified as Responders (R), Partial-Responders (PR) and Non- Responders (NR). Results: Seventeen patients (54.8%) had a complete metabolic response (R), 4 (12.9%) were PR while 10 (32.3%) had no Metabolic Response (NR). The chi-square test showed that response groups were related neither to the stage of disease (p=0.59) nor to therapy performed (p<0.079). The comparison between each Δ semiquantitative parameter showed a statistically significant decrease from PET1 to PET2 (0.0001 < p < 0.002). The comparison between Δ mean values in relation to response groups showed to be statistically significant (0.001 < p < 0.005). Conversely, they did not show statistical significance in relation to the clinical stage groups and to the kind of therapy performed (p>0.05). Pearson’s coefficient demonstrated a reverse correlation between a number of sites still involved in disease after therapy and each Δ semiquantitative parameters (p≤0.0001). Conclusion: 18F-FDG PET/CT should be considered a useful technique for the evaluation of sarcoidosis and semiquantitative parameters. Further studies are needed to determine the long-term impact of 18F-FDG PET/CT on clinical outcomes.