ABSTRACT
Gadolinium-enhancing lesion counts have become standard measures in clinical trials in multiple sclerosis (MS), providing an index of inflammatory activity around the time of the magnetic resonance imaging (MRI) study, as well as a cumulative index of disease activity over intervals when used in a serial monthly MRI scan format. As MS therapies, both approved and experimental, target the inflammatory aspects of the disease, counts of enhancing lesions provide a sensitive, convenient, and rational measure of efficacy. As a result, enhancing lesion measures have become primary outcome measures in many phase II trials. In phase III trials, counts of enhancing lesions are recorded either at halfyearly or yearly intervals to determine residual inflammation as a secondary outcome measure or at monthly intervals in a subset of patients to evaluate potential short-term effects of therapy. More recently, counts of enhancing lesions have been introduced into phase I trials as a safety measure.
