Therapeutic efficacy of tocilizumab in patients with rheumatoid arthritis refractory to anti-tumor-necrosis-factor inhibitors: 1 year follow-up with low-field extremity MRI

Abstract

Tocilizumab (TCZ) is effective in patients with rheumatoid arthritis (RA) who are refractory to anti-tumor-necrosis-factor (anti-TNF) biologics. The Rheumatoid Arthritis Society Disease Activity Score in 28 Joints (DAS28) is used to evaluate the response to TCZ. However, DAS28 is inappropriate marker because TCZ normalizes C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in the early stage of treatment. The aim of our study was to test the usefulness of magnetic resonance imaging (MRI)-based markers of response to TCZ treatment. Nine patients with RA who were refractory to anti-TNF inhibitors (six to infliximab, one to etanercept, one to adalimumab, and one to both) were assessed. MRI images of both hands were obtained by low-field extremity MRI at baseline, 20, and 44 weeks of treatment, in addition to assessment with DAS28-ESR. The effect of TCZ on RA was examined by compact MRI score (cMRIS). All patients showed good or moderate response to TCZ treatment, as evaluated by significant reduction in DAS28-ESR at both 20 and 44 weeks (p < 0.001, each, relative to baseline). In contrast, MRI-based indexes (e.g., cMRIS, synovitis, edema, erosion scores) improved significantly at 44 weeks but not at 20 weeks. Differences in response to TCZ therapy were determined based on the method of evaluation, suggesting that MRI-based markers are potentially useful for evaluating RA response to TCZ therapy.