MRI metrics as surrogate markers for clinical relapse rate in relapsing-remitting MS patients

Objective: To formally validate metrics derived from conventional MRI as surrogate endpoints for relapse rate in MS. Background: Although metrics derived from MRI are used widely in clinical trials of MS, a formal statistical validation of MRI metrics as surrogate endpoints for clinical outcome in MS is lacking. Methods: A validation procedure was applied to clinical and MRI data collected in the context of a randomized, double-blind, placebo-controlled trial of glatiramer acetate in patients with relapsing-remitting MS. The four Prentice operational criteria were applied to assess surrogacy for the number of new enhancing lesions, the percentage change of T2 lesion volume, and a composite MRI score based on these two metrics. Results: The results of this analysis show that all three MRI measures considered by the authors had a behavior compatible with the Prentice criteria for valid surrogates. The composite MRI score correlated with relapses and accounted for much of the treatment effect on relapse rate. Conclusion: This preliminary study suggests that conventional MRI metrics might serve as valid surrogate endpoints in MS trials with glatiramer acetate or treatments thought to have a similar mode of action.