The use of MRI as an outcome measure in clinical trials.

Because the changes on MRI likely reflect various aspects of the underlying pathology of multiple sclerosis, MRI outcome measures have become an important component of most MS clinical trials, providing objective, supportive evidence for the clinical endpoints. Although there is currently insufficient evidence to support any single or combination of MRI measures as a fully validated surrogate, it is now generally accepted that if the aim of a new therapy is to prevent relapses, new Gd-enhancing and T2 lesions can be considered an appropriate surrogate outcome measure of relapses, and MRI activity outcomes can be recommended as the primary measure of treatment efficacy.