MRI comes of age in RA clinical trials.

The success of modern rheumatoid arthritis (RA) therapies and treatment strategies has led to extended placebo phases being unethical in RA randomised controlled trials (RCTs). Modern trials therefore increasingly involve active comparator designs, and this together with some technical issues has meant difficulties in differentiating structural progression using traditional radiographic outcome measures. Magnetic resonance imaging (MRI) has been demonstrated to assess damage more sensitively than radiographs, but importantly it can measure the upstream drivers of erosions and cartilage loss, synovitis and osteitis. An increasing number of recent RCTs using the RA MRI scoring system (RAMRIS) have demonstrated the ability of MRI to discriminate progression and treatment effect. Consistency of erosion progression determination was seen across the majority of these studies. In most studies, MRI demonstrated reduction in synovitis and osteitis at early (12 week) timepoints, and MRI predicted subsequent radiographic findings. Often small numbers of patients were required to demonstrate such changes. The time is right for regulatory authorities to include MRI as an alternative to radiographic data in support of claims of inhibition of progression of structural damage in RA trials.