Background/Purpose: One of the important therapeutic goals in patients with rheumatoid arthritis (RA) is to halt radiographic progression. Tocilizumab (TCZ), an IL-6 receptor antibody, has been demonstrated that it efficiently improves clinical signs and inhibits structural damages in RA patients. However, it remains unknown what the predictive factor is for long-term radiographic outcomes in RA patients receiving TCZ. The objectives of this study are to assess the structural remission rate and to clarify the predictive factor for long-term radiographic outcomes in patients receiving TCZ under daily clinical practice.

Methods: Michinoku Tocilizumab Study Group comprised 34 institutions in the Northeast region of Japan. RA patients who received 8 mg/kg TCZ every 4 weeks were registered from June 2008 to December 2010 [1]. The clinical and radiographic outcomes were evaluated in 130 patients at 1 year, including 50 patients who received TCZ for 3 years.

Results: Baseline characteristics of patients who received TCZ for 1 year and 3 years, respectively, were as follows: mean age of 59.7/ 58.0 years, the mean disease duration of 10.8/ 10.9 years, the mean DAS28-ESR of 4.8/ 4.8, and 37.7/ 36.0% of patients were taking MTX. Mean change from baseline in van der Heijde-modified total Sharp score (mTSS) was 0.79 at 1 year, and the structural remission rate (ƒ¢mTSS≤0.5) was 69.2%. In the 50 patients who received TCZ for 3 years, the structural remission rate for 3 years (ƒ¢mTSS≤1.5) was 66%. Radiographic benefit gradually increased as the structural remission rate at the first, second, third year was 68.6%/78.6%/88.9%, respectively (Figure 1). At baseline, not tender joint counts (p=0.58), but swollen joint counts (SJC, p=0.04) predicted the structural remission at 3 years. Receiver Operating Characteristic (ROC) analysis showed that the cut-off value of SJC at baseline for structural remission at 3 years was 5. Even when SJC at baseline were above 5, SJC at 9 months (p=0.02) and at 12 months (p=0.004) were good predictors for structural remission at 3 years.

Conclusion: TCZ continuously inhibited radiographic progression in RA patients. SJC within a year could predict long-term radiographic outcomes irrespective of baseline disease activity in patients receiving TCZ.

References: [1] Hirabayashi Y, Ishii T, and the Michinoku Tocilizumab Study Group. The DAS28-ESR cutoff value necessary to achieve remission under the new Boolean-based remission criteria in patients receiving tocilizumab. Clin Rheumatol. DOI 10.1007/s10067-012-2103-4.