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POS1379 HYPERMETABOLIC BONE SARCOIDOSIS ON 18F-FDG PET-CT: IMPACT ON TREATMENT AND DISEASE RELAPSE IN A COHORT OF 165 PATIENTS FROM A SINGLE UNIVERSITY HOSPITAL

Sarcoidosis is a multisystemic granulomatosis of unknown cause. Prevalence of bone sarcoidosis is estimated between 3 and 30%. Bone sarcoidosis is symptomatic in about half of the cases. 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is a useful imaging modality in sarcoidosis, to search for a biopsiable site, evaluate organ involvement or assess disease activity. It is a sensitive imaging modality to detect bone involvement. However, clinical and prognostic significance of hypermetabolic bone involvement of sarcoidosis is not well known.The aim of this study was to compare the characteristics of patients with and without hypermetabolic bone involvement of sarcoidosis and to evaluate the impact of metabolic bone involvement on treatments and outcomes.This was an observational, comparative, retrospective monocentric study of prospectively collected data. Inclusion criteria were a diagnosis of sarcoidosis according to the World Association of Sarcoidosis and Other Granulomatous diseases (WASOG) criteria and at least one 18F-FDG PET-CT during follow-up. Metabolic bone involvement of sarcoidosis was defined as bone hypermetabolism for which alternative causes had been reasonably excluded, following the WASOG criteria of « at least probable » bone sarcoidosis. Characteristics of patients with and without bone involvement were compared using bilateral Fisher or Mann-Whitney tests. Relapse-free survival curves were constructed following the Kaplan-Meier method and compared using a log-rank test. A p-value < 0.05 was considered significant.Among 503 patients with sarcoidosis, 165 with definite sarcoidosis who had undergone at least one 18F-FDG PET-CT were included. Fourteen patients had positive bone PET-CT findings which were attributed to other cause than sarcoidosis. Metabolic bone involvement of sarcoidosis was found in 29 patients (18%), among which 9 (31%) had structural bone lesions on CT. Metabolic bone involvement of sarcoidosis was associated with more frequent intrathoracic lymph node involvement (28 [96%] and 107 [79%], p < 0.001), extrathoracic lymph node involvement (15 [52%] and 40 [30%], p = 0.03) and a higher number of organ involvements (median [interquartile range], 6 [4-7] and 4 [2-5], p < 0.001). Patients with metabolic bone involvement received more frequently corticosteroids (29 [100%] and 99 [73%], p < 0.001), methotrexate (26 [90%] and 66 [48%], p < 0.001), tumor necrosis factor (TNF) alpha inhibitors (22 [76%] and 41 [30%], p < 0.001), and a higher number of treatments (3 [3-4] and 2 [1-3], p < 0.001). Despite more intensive treatments, disease relapse occurred significantly sooner in patients with metabolic bone involvement of sarcoidosis (median time to the first relapse, 63 [44-84] months and 96 [72-156] months respectively, p = 0.01).Metabolic bone involvement on PET-CT was present in 18% of patients with sarcoidosis. It was predominantly axial and without structural lesions. In this comparative study, patients with metabolic bone involvement received significantly more treatments and had a shorter time to relapse. It could therefore reflect a more severe multisystemic involvement and chronic evolution of the disease. This could help adjust individual therapeutic strategy for patients with sarcoidosis.[1]Challenges of Sarcoidosis and Its Management. Drent M, Crouser ED, Grunewald J. N Engl J Med. 2021 Sep 9;385(11):1018-1032.[2]Clinical Presentation and Treatment of High-Risk Sarcoidosis. Perlman DM, Sudheendra MT, Furuya Y, Shenoy C, Kalra R, Roukoz H, Markowitz J, Maier LA, Bhargava M. Ann Am Thorac Soc. 2021 Sep 15. doi: 10.1513/AnnalsATS.202102- 212CMEFigure 1.None declared