Background Tumor necrosis factor-α (TNF-α) inhibition has been evolutionary in the treatment of ankylosing spondylitis (AS). Conventional radiography reflects chronic structural damage in AS rather than the underlying inflammatory processes that lead to bone damage. The use of magnetic resonance imaging (MRI) addresses the need for a more objective measure of disease activity and response to therapeutics in AS.
Objectives To investigate the effectiveness of infliximab, a TNF-α inhibitor, on structural damage progression in AS using MRI.
Methods Thirty-one patients (21 men and 10 women) suffering from AS with a median (IQR) age at baseline 39 (29-48) years and a median (IQR) disease duration 3 (1.0-11.5) years were included in this prospective, open label study. All patients had active axial disease with a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score ≥4 cm. They were all refractory to at least 3 months of therapy with non-steroidal anti-inflammatory drugs and naïve to anti-TNFa therapy at recruitment. Infliximab was given intravenously at a dose 5mg/kg at weeks 0, 2, 6 and every 8 weeks thereafter. MRI scans of the sacroiliac (SI) joints were obtained at baseline and after one year of infliximab therapy. The MRI scans were scored by a radiologist with musculoskeletal expertise according to modified Spondyloarthritis Research Consortium of Canada score. The scorer was blinded to clinical data.
Results All patients completed 12 months of infliximab therapy. Infliximab therapy resulted in a significant reduction of BASDAI [median (IQR) BASDAI at baseline 4.8 (4.40-5.12) vs 0.95 (0.45-1.90) at 12 months (p=0.001)] and in a parallel decrease of C-reactive protein [7 (2-16) vs 3 (2-8) (p=0.031)]. As regards the acute lesions in SI joints detected by MRI, a significant resolution of their total score was noticed [3 (0-7) vs 0 (0-1) p=0.001]. More specifically, infliximab therapy induced a significant improvement both in MRI synovitis score [0 (0-1) vs 0 (0-0) p=0.009] and in MRI bone edema score [3 (0-7) vs 0 (0-1) p=0.001] over time. On the other hand, in total, the chronic lesions in SI joints detected by MRI increased significantly during the observational period [12.0 (8.0-16.0) vs 15.5 (10.5-18.0) p=0.024]. However, a detailed analysis showed that apart from MRI fatty bone marrow depositions score which was augmented during the study [6 (4-8) vs 8 (5-12) p=0.006], the other chronic lesions remained stable: MRI erosions score [2 (0-4) vs 3 (0-4) p=0.183], MRI subchondral sclerosis score [1 (0-3) vs 1 (0-3) p=0.481] and MRI ankylosis score [0 (0-1) vs 0 (0-1) p=0.785].
Conclusions In our AS patients, infliximab therapy offered a significant clinical improvement accompanied by a regression of acute MRI lesions of sacroilitis. Furthermore, infliximab halted the progress of pre-existing erosions, sclerosis and ankylosis of SI joints. The increase in MRI fatty bone marrow depositions score should not be considered as a structural deterioration since these depositions reflect sites of non-active inflammation in the context of convalescence.
Disclosure of Interest None declared