AB1455 FLUORIDE UPTAKE ON QUANTITATIVE POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY (NA18F-PET/CT) AS NOVEL BIOMARKER FOR DISEASE ACTIVITY IN ADULT CHRONIC NONBACTERIAL OSTEOMYELITIS/SYNOVITIS ACNE PUSTULOSIS HYPEROSTOSIS OSTEITIS SYNDROME (CNO/SAPHO)

Background Chronic nonbacterial osteomyelitis (CNO) is a rare bone disease characterized by sterile inflammation and locally increased turnover. CNO that occurs in the rheumatic spectrum of synovitis, acne, pustulosis, hyperostosis osteitis referred to as SAPHO syndrome [1, 2]. To date, there are no objective biomarkers for monitoring activity. Recommended imaging tools like technetium radiolabeled hydroxymethylene diphosphonate single positron emission computed tomography visualize turnover, but fail reflect relapsing-remitting activity course due an imprinting pattern [3]. Likewise, magnetic resonance can track fluctuation marrow edema, inferior compared (CT) capturing subtle inflammatory accumulated structural changes duration. Sodium fluoride-18 tomography/CT(Na 18 F-PET/CT) another modality which produces quantitative data on spatial distribution turnover also correlate with clinical other metabolic diseases [4]. Objectives We quantified F-uptake CNO/SAPHO patients evaluate its capacities biomarker. Methods Cohort study including 43 not using immunomodulatory or antiresorptive medications Na F-PET/CT performed at our expert clinic between 2019-2022. Images were qualitatively assessed following systematic reporting format. Maximal standardized uptake values (SUV max ) determined areas defined radiologic appearance CT: osteitic (osseous lesions), inflamed ligaments joint spaces (soft tissue lesions) thoracic vertebrae 5 reference (ref-bone). Results Qualitative assessment revealed sclerosis manubrium most prevalent features (present 77% 70%) costae 1-2 (79% each). Calcification/ankylosis costoclavicular ligament was seen 58%. Quantitative analyses showed higher SUV osseous soft lesions ref-bone (mean 22±6 26±9 vs. 11±3 g/mL, p<0.001 paired difference). Stratified per location, highest found followed manubriosternal 29±13 25±8 respectively). positively correlated erythrocyte sedimentation rate (Spearman correlation coefficient 0.546, p<0.01 ). Conclusion display distinctive qualitative well-captured F-PET/CT, show ref-bone. Diseased . Considering F precipitates young osteoid, these high may process ossification common long-existing CNO/SAPHO, demonstrated fibrodysplasia ossificans progressiva [5]. Further studies should promising application novel biomarker therapy response CNO/SAPHO. References [1]Leerling et al. Clinical therapeutic diversity adult chronic sternocostoclavicular region: meta-analysis. Rheumatology 2022. [2]Rukavina I. syndrome: review. J Child Orthop 2015. [3]Li A retrospective scintigraphy follow-up it useful repeat assessment? 2019. [4]van der Bruggen Quantifying skeletal burden fibrous dysplasia sodium fluoride PET/CT. Eur Nucl Med Mol Imaging 2020. [5]Botman Evolution heterotopic progressiva: An [(18)F]NaF PET/CT study. Bone Acknowledgements: NIL. Disclosure Interests None Declared.