POS0807 IMPROVEMENT OF BONE MINERAL DENSITY AND NEW VERTEBRAL FRACTURES DURING 8 YEARS OF TNF-Α INHIBITION IN PATIENTS WITH AXIAL SPONDYLOARTHRITIS
Authors: M. Siderius, F. Wink, S. Kieskamp, F. Maas, R. Bos, F. G. M. Kroese, J. P. L. Spoorenberg, S. Arends
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease which mostly develops in young adults and predominantly affects the axial skeleton. Both excessive bone formation of the cortical bone and loss of bone density of the spongy bone are frequently observed in the axial skeleton, and bone-related outcomes are often negatively impacted in axSpA [1]. Previous studies showed significant improvement in bone mineral density (BMD) at the lumbar spine (LS), but radiographic vertebral fractures (VFs) still occurred during the first years of treatment with tumor necrosis factor-alpha inhibitors (TNFi) [2]. <h3>Objectives:</h3> Our aim was to evaluate the course of BMD and the development of radiographic VFs during 8 years of TNFi treatment in patients with axSpA. <h3>Methods:</h3> Consecutive axSpA patients from the GLAS cohort receiving TNFi for ≥8 years were included. Patients who received anti-osteoporotic treatment were excluded. LS BMD was assessed at baseline, 1 year and bi-annually using DEXA. Generalized estimating equations were used to analyze BMD Z-scores over time within subjects. Radiographic VFs were evaluated using the Genant classification. <h3>Results:</h3> 126 axSpA patients were included; the vast majority (97%) had r-axSpA, 75% were male, mean age was 42±11 years, mean ASDAS was 3.8±0.8, median LS BMD Z-score was -0.5 (IQR -1.4-0.7) and 20% had radiographic VFs at baseline. As expected, after start of TNFi, disease activity showed a rapid and sustained improvement (mean change in ASDAS was 1.7 ± 1.1 after 8 years). LS BMD Z-score improved significantly up to 4 years compared to the previous time point and sustained thereafter (Figure 1). Median percentage of improvement compared to baseline was 8.9% (2.8-15.8) and 7.2% (2.2-14.7) after 4 and 8 years, respectively. Of 90 patients with available radiographs, 14 (16%) developed at least one new VF and 5 (6%) showed an increase in severity of existing VFs. Of the in total 44 VFs present at 8 years follow-up, 31 were defined as mild, 12 as moderate and one as severe. All fractures except three were observed in the middle and lower thoracic spine (Figure 2). Patients with new or progressing VFs had a large variation in age (range 21-67 years) and 72% of patients was &lt;50 years. Of the five patients who progressed to clinically relevant VFs (grade 2-3), four demonstrated severe spinal radiographic damage and one patient without spinal radiographic damage had low BMD with little improvement during TNFi treatment. <h3>Conclusion:</h3> In our cohort of r-axSpA patients treated with TNFi for 8 years in daily clinical practice, LS BMD increased significantly, especially during the first 4 year of treatment and stabilized thereafter. However, new or progression of radiographic VFs was still observed. <h3>REFERENCES:</h3> [1] Klingberg et al. Arthritis Res Ther. (2013);15(6):R179. [2] Maas et al. Clin Exp Rheumatol. 2016 Mar-Apr;34(2):191-9. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> Mark Siderius Consultant for Novartis, Freke Wink Consultant for Novartis, Abbvie, Stan Kieskamp: None declared, Fiona Maas: None declared, Reinhard Bos Speaker for Galapagos, Janssen, Consultant for Abbvie, Galapagos, Pfizer, UCB, Research grants from Sanofi, Galapagos, Frans G.M. Kroese Speaker for BMS, Roche, Janssen-Cilag, Research grant from BMS, J.P.L Spoorenberg Consultant for Novartis, Abbvie, Pfizer, UCB, Galapagos, Research grant from Novartis, Suzanne Arends Consultant for Argenx, Novartis, BMS, Galapagos.