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.

Objective: 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.

Methods: 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).

Results: 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.

Conclusion: 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.