MRI and clinical activity in MS patients after terminating treatment with interferon beta-1b

Monthly MRI activity and clinical disability were evaluated in two relapsing-remitting multiple sclerosis (RRMS) patients for 4 years during a cross-over treatment trial with IFNbeta-1b, and for a mean of 21 months after terminating treatment with IFNbeta-1b. Post-treatment MRI activity was compared to baseline activity in these patients. Although contrast enhancing lesions (CEL) and the bulk white matter lesion load (BWMLL) on T2-weighted images eventually returned to baseline values, there was a refractory period of 6 - 10 months after terminating treatment, before baseline MRI activity was restored. Although the mechanism for a sustained effect of IFNbeta-1b is unclear at this time, these results have important implications for enrollment of such patients into new treatment protocols that rely on contrast enhancing lesion frequency as an outcome measure.