68Ga-FAPI PET/CT for assessing fibroblast activation and disease activity in primary Sjögren's disease: a prospective case-control study.

Abstract

ObjectiveSjögren's disease (SjD) is an autoimmune exocrinopathy characterized by chronic glandular inflammation. Fibroblast activation protein (FAP) is a promising imaging biomarker for local inflammation. This study aims to evaluate the utility of [68Ga]Ga-FAPI PET/CT in SjD, assess its correlation with disease activity, and explore its role in monitoring treatment response.MethodsThis study enrolled SjD patients (2016 ACR-EULAR criteria), with cancer patients as controls. All SjD participants underwent EULAR Sjögren's Syndrome Patient Reported Index and EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) assessments and serological testing; labial gland biopsies were additionally performed in a subset. The enrolled patients subsequently underwent longitudinal follow-up.Results[68Ga]Ga-FAPI-04 PET/CT imaging revealed significantly higher tracer uptake in the lacrimal, parotid and sublingual glands of SjD patients compared with controls (all P Conclusion[68Ga]Ga-FAPI PET/CT noninvasively assesses fibroblast activation in SjD, correlates with disease activity and treatment response, and supports its potential clinical utility.Trial registrationThis study has been registered online at NIH ClinicalTrial.gov (NCT07062523).