CORRELATIONS BETWEEN MONTHLY ENHANCED MRI LESION RATE AND CHANGES IN T2 LESION VOLUME IN MULTIPLE-SCLEROSIS

Magnetic resonance imaging (MRT) provides a powerful tool for assessin g disease activity in multiple sclerosis (MS), and its role as a surro gate marker for monitoring treatment efficacy is now becoming establis hed. The most commonly used MRI parameters in treatment trials are (1) monthly gadolinium-enhanced MRI, with the number of active lesions se rving as the outcome measure, and (2) annual lesion load quantificatio n, in which change in MS lesion volume provides the MRI endpoint. We e valuated clinical/MRI correlations and the relationship between these two markers of disease activity in 73 patients with clinically definit e MS. Quantification of T2 lesion load was performed at study entry an d exit, with a median study duration of 11 months (range, 9 to 14 mont hs). Monthly postgadolinium T1-weighted images were acquired between t hese time points. Lesion load at study entry was significantly correla ted with the baseline Expanded Disability Status Scale (EDSS) score, b ut no significant longitudinal correlation was demonstrated. The numbe r of enhancing lesions on the entry scan was predictive of subsequent relapse rate over the study duration and also correlated with the subs equent enhancing lesion activity over the study period. A significant correlation was found between change in lesion load and disease activi ty on the monthly scans. Our results suggest that annual lesion load q uantification provides an efficient measure of ongoing disease activit y, and this supports its application as a surrogate marker of disease evolution in phase III treatment trials.