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SAT0240 New Inflammatory Lesions in Axial Spondyloarthritis are More Likely to Occur in the Areas Already Affected by Inflammation in the Past

Background Axial spondyloarthritis (axSpA) is characterised by a substantial fluctuation of inflammation with resolution and new occurrence of inflammatory lesions in the course of the disease. However, it is not clear, whether new osteitis lesions as detected by magnetic resonance imaging (MRI) occur on random or there are factors predicting a certain localisation of new lesions. Objectives To investigate the localisation of newly occurred osteitis lesions in the sacroiliac joints (SIJ) and in the spine in patients with early axSpA in the Part II of the Infliximab As First Line Therapy in Patients with Early Active Axial Spondyloarthritis Trial (INFAST) [1]. Methods Part I of the INFAST study was a double-blind, randomized controlled trial of infliximab (IFX) - Remicade – in patients with early (<3 years symptom duration), active axSpA with signs of active sacroiliitis on MRI. A total of 158 patients were randomized (2:1) to receive 28 weeks of treatment with either intravenous IFX + naproxen (NPX) or intravenous placebo (PBO)+NPX. In Part II of INFAST, patients who had achieved ASAS partial remission at week 28 - W28 (n=82) were randomized in a 1:1 ratio to continue on NPX 1000 mg/d alone or to stop NPX until week 52 - W52. MRIs of the SIJ and of the spine in STIR and T1-weighted sequences performed at baseline, W28 and W52 were scored according to the Berlin scoring system for active inflammation and for fatty lesions [2]. Results At W28 (end of part I, the new baseline for part II), osteitis was present in 13.1% vs. 14.3% SIJ quadrants and 3.2% vs. 5.2% VUs in the NPX vs. no treatment groups, respectively. At W52, 39.2% vs. 28.7% of SIJ quadrants (p=0.008) and 8.1% vs. 14.0% of VUs (p<0.001) in the NPX vs. no treatment groups, respectively, were affected by inflammation. New osteitis lesions at W52 were more frequent in the NPX group in the SIJ (30.8% vs. 22.0%, p=0.03) but less frequent in the spine (5.6% vs. 11.3%, p<0.001). Osteitis at W52 in the SIJ occurred more frequently in the quadrants with fatty lesions observed at W28 (30%) as compared to those quadrants without any lesions at W28 (15.4%) – table. However, presence of inflammation at W0 (that disappeared at W28 due to the treatment in the phase I of the study) was even a stronger predictor of new osteitis at W52, which occurred in 39.2% of the quadrants affected by osteitis at W0 as compared to 13.8% of the quadrants without osteitis at W0. Presence of fatty lesions at W0 was not significantly associated with new osteitis lesions later on - table. Similarly for the spine, new osteitis lesions at W52 occurred more frequently in VUs with fatty lesions at W28 as compared to VUs without any lesions (21.3% vs. 5.7%); also fatty lesions at W0 was significantly associated with new osteitis lesions at W52 – table. However, the highest risk of new osteitis lesions at W52 was associated with osteitis observed at W0: new lesion occurred at W52 in 43.9% of VUs with osteitis at W0, as compared to 3% of the VU without previous osteitis - table. Conclusions Naproxen therapy did not prevent occurrence of new inflammatory lesions. New inflammatory lesions in axial spondyloarthritis are more likely to occur in the areas already affected by inflammation in the past. References Sieper J, et al. Ann Rheum Dis 2014;73:101-7. Althoff CE, et al. Ann Rheum Dis 2013;72:967-73. Acknowledgements The MRI analysis substudy was supported by an unrestricted research grant from MSD. Disclosure of Interest D. Poddubnyy Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB, J. Sieper Grant/research support from: Abbvie, MSD, Pfizer, Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB