Using 18F-FDG and 68Ga-PSMA-11 PET/CT to evaluate salivary glands in Sjögren's Disease: Implications for Treatment Stratification

Abstract

Abstract Objectives To investigate the associations of ¹⁸F-FDG PET/CT and ⁶⁸Ga-PSMA-11 PET/CT parameters with salivary gland ultrasonography abnormalities and unstimulated whole salivary flow rate in patients with Sjögren’s disease. Methods Twenty-three patients with SjD who had undergone ¹⁸F-FDG PET/CT within the previous 6 months subsequently underwent ⁶⁸Ga-PSMA-11 PET/CT. FDG SUVmax, FDG SUVmean, PSMA SUVmax, PSMA SUVmean, PSMA-based functional glandular volume (PSMA-GIVol), and PSMA-based total glandular activity (PSMATotGlAct; PSMA SUVmean × PSMA-GIVol) were calculated for each parotid and submandibular gland and compared with SGUS scores and UWSFR. Results PSMA SUVmax, PSMA SUVmean, and PSMATotGlAct were lower in glands with higher SGUS scores, while PSMA-GIVol showed a decreasing trend, particularly in the submandibular glands. FDG uptake showed gland-dependent patterns: higher uptake was observed in parotid glands with higher OMERACT and selected Hocevar abnormalities, whereas lower uptake was observed in submandibular glands with higher OMERACT and hypoechoic area scores. UWSFR showed no significant association with ⁶⁸Ga-PSMA-11 PET/CT parameters, but correlated positively with FDG uptake in both parotid and submandibular glands. Conclusion ⁶⁸Ga-PSMA-11 PET/CT and ¹⁸F-FDG PET/CT appear to provide complementary information in SjD. Lower PSMA uptake may reflect structural glandular damage, whereas FDG uptake patterns, particularly their association with preserved salivary flow, may indicate residual metabolic activity and retained functional potential.