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Purpose:
X-rays are commonly used to image RA treatment effects in clinical studies but can only monitor the late stage disease effects of bone erosions. MRI, however, has the potential to detect the inflammatory components of RA such as synovitis, and tissue and bone edema. RA treatments target these inflammatory effects, so MRI has the potential to detect efficacy much earlier. The goals of this study were to determine the impact of short term anti-TNF therapy on changes to quantitative and semi-quantitative image endpoints in the MCP joints.
Method:
Prior to starting anti-TNF therapy (open-label) 22 RA subjects, at 4 centers, who were on a stable background therapy of methotrexate, were scanned on an OrthoOne 1.0T peripheral MRI scanner. Scans were repeated at 4, 8 and 12 weeks of treatment. MCP joints were imaged with the following sequences: Coronal T2 fat suppressed FSE, coronal and axial 3D GRE, and 2D axial dynamic contrast enhanced (DCE) SPGR acquired continuously starting before bolus injection of 0.1 mmol/kg Gd-DTPA and continuing for 4 minutes.
For all subject visits the semi-quantitative ACR20, EULAR-OMERACT and DAS28 – 3CRP scores were determined. Semi-automated segmentation of the MRI was used to calculate the enhancing synovium, enhancing tissue (synovium, bone, tendons and muscle). Bone edema counts were determined by the average number of distinct edema regions. DCE MRI was used to calculate the initial area under the curve (IAUC) for the enhancing synovium and tissue. All MRI endpoints evaluated the 2nd -5th MCP joints.
Statistical significance was obtained by modeling the log of the follow-up to week 0 ratio of the measure. P < 0.05 was significant.
Results:
The figure shows the mean and standard error bars for each of the measures at 0, 4, 8, and 12 weeks for the 20 of 22 completing subjects. Only a few of the subjects presented with bone edema, so error bars and significance of change were not calculated. Most measures showed a trend for reduction over 12 weeks but only the OMERACT synovitis score at week 12 and the DAS scores at week 4, 8 and 12 were significant. The OMERACT synovitis score at week 8 and the enhancing synovium volume at week 12 showed a decreasing trend.
Conclusion:
The ACR20 response rate at week 12 was unexpectedly low compared to similar anti-TNF studies. This may have also resulted in a lower response rate for the inflammatory MRI biomarkers. However, the DAS-28 and OMERACT synovitis scores showed a statistically significant treatment response