Exploring the Novel Value of PSMA PET in Sjögren's Syndrome: Integrated Analysis With Established FAPI PET Imaging

Chinese Academy of Medical Sciences & Peking Union Medical College

Status: Enrolling

Conditions: PET; Primary Sjögren Syndrome

Treatments: Diagnostic Test: ⁶⁸Ga-FAPI PET/CT; Diagnostic Test: ⁶⁸Ga-PSMA PET/CT

Study type: Interventional

Funder types: Other

Identifiers

NCT07324733

PUMCH-PSS-PSMA

Details and patient eligibility

About

Primary Sjögren's syndrome (pSS) is a chronic autoimmune exocrinopathy characterized by lymphocytic infiltration, progressive destruction of salivary gland acini, and varying degrees of functional impairment and fibrosis. Conventional imaging provides limited ability to simultaneously evaluate glandular function and inflammatory activity, leading to challenges in disease staging and treatment decision-making. This study explores a conceptual dual-tracer imaging framework using PSMA PET and FAPI PET to delineate complementary biological processes in pSS.

Full description

Based on current evidence, salivary gland acinar cells physiologically express PSMA; thus, reduced PSMA uptake may reflect loss of functional parenchyma in patients with pSS. In contrast, activated fibroblasts markedly express FAP, and increased FAPI uptake correlates with ongoing inflammation and fibroblast-driven remodeling. We hypothesize that within the same gland, functional decline (PSMA↓) and inflammatory activity (FAPI↑) may coexist and exhibit a negative correlation, forming a paired imaging biomarker that captures both pathological dimensions. By integrating these two signals into a combined PSMA/FAPI Index, this approach may enable more precise characterization of the "function-inflammation" spectrum in pSS, providing a noninvasive tool for disease staging, monitoring, and potentially predicting therapeutic response.

Enrollment: 60 estimated patients

Sex: All

Ages: 18 to 80 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Age 18-80 years;
• Fulfillment of the 2016 ACR-EULAR Classification Criteria for pSS at enrollment. OR diagnosis of a solid tumor scheduled for FAPI PET imaging

Exclusion criteria

• Combined with tumors or other connective tissue diseases (for SS group);
• Patients who are currently using hormones/biological agents (for both groups)；
• Pregnancy or lactation

Trial design

Primary purpose: Diagnostic

Allocation: Non-Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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60 participants in 2 patient groups

pSS Dual-Tracer Imaging Arm (PSMA + FAPI PET)

Experimental group

Description:

This arm includes patients diagnosed with primary Sjögren's syndrome. All participants undergo both PSMA PET and FAPI PET imaging. The PSMA PET scan is used to assess the functional integrity of salivary gland acinar cells, while the FAPI PET scan evaluates inflammatory and fibroblast activity within the same glands. The purpose of this arm is to characterize the functional-inflammatory relationship in pSS and to develop the combined PSMA/FAPI Index for disease staging and activity assessment.

Treatment:

Diagnostic Test: ⁶⁸Ga-PSMA PET/CT

Diagnostic Test: ⁶⁸Ga-FAPI PET/CT

Prostate Cancer PSMA-Only Comparator Arm

Active Comparator group

Description:

This arm consists of patients with prostate cancer who undergo PSMA PET imaging only, representing a population with preserved or physiologic salivary gland PSMA uptake. These scans serve as a reference group for establishing normal or baseline PSMA expression in salivary glands. This comparator arm allows differentiation between disease-related PSMA reduction in pSS and normal tracer distribution observed in patients without salivary gland pathology.

Treatment:

Diagnostic Test: ⁶⁸Ga-PSMA PET/CT