Usefulness of 18F-FDG PET-CT in detecting subclinical arteritis and cancer associated with polymyalgia rheumatica.

Objective: To assess the prevalence of giant cell arteritis (GCA) or cancer detected via 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) in patients with polymyalgia rheumatica (PMR) without clinical signs suggestive of GCA.

Method: This monocentric retrospective cohort study analyzed PET-CT scans performed for clinical suspicion of PMR since 2018. Patients meeting the 2012 ACR/EULAR criteria for PMR without clinical indications of GCA or cancer were included. Observations were divided into two groups: new-onset PMR and treatment failure. A nuclear medicine physician evaluated qualitative liver uptake scores at articular/periarticular sites and large vessels typically involved in PMR. Increased 18F-FDG uptake suggesting cancer was also assessed.

Results: Of 1223 PET-CT scans screened, 94 met the inclusion criteria: 38 for new-onset PMR and 56 for treatment failure. Subclinical GCA was identified in 10 (10.6%) patients, with a prevalence of 5.3% in the new-onset group and 14.2% in the treatment failure group. Aortic uptake was present in 90% of subclinical GCA cases. Sites with increased 18F-FDG uptake included hips (90%), shoulders, lumbar interspinous bursa (80%), and ischial tuberosity (60%). PET-CT identified eight (8.5%) cancer cases, equally distributed between the two groups.

Conclusion: PET-CT detects subclinical GCA in approximately 10% of PMR patients without suggestive symptoms, three times more frequently in the treatment failure group. Aortitis is present in 90% of subclinical GCA cases. Cancer prevalence is 4.7%, with a heterogeneous spectrum and unclear association with PMR symptoms.