Is radiographic progression a realistic outcome measure in clinical trials with early inflammatory arthritis?

Radiographic progression is one of the most important outcome measures in rheumatoid arthritis (RA) clinical trials, because it reflects historic disease activity, is associated with loss of function over time, and can be reliably assessed. Trials involving patients with early inflammatory arthritis (EIA) will differ from those focusing on RA patients in many respects. They include a heterogeneous spectrum of patients, and some of them will have self-limiting arthritis, or arthritis with a low likelihood of ever becoming erosive. Furthermore, because of the early presentation a high proportion of patients with a high likelihood of erosions will still be non-erosive at presentation; and since EIA trials will aim at permanent clinical remission induced by therapy, the signs of progression will be very subtle. Current radiographic scoring methods may not be sensitive to the small changes that are expected to occur in EIA trials. This makes radiographic progression a rather unlikely single primary outcome in such trials. However, "permanent clinical remission" (with or without therapy) appears to be a most realistic outcome in such trials, and radiographic stability (the demonstration of "no progression") may serve as a key criterion in establishing whether the endpoint of permanent clinical remission is actually met. The moment at which the first erosion develops is also important in making the correct diagnosis and has implications for the prognosis. We propose here a number of recommendations for the use of radiographic progression as one of the obligatory outcome measures in clinical trials with EIA.