Effect of interferon beta-1b in MS - Assessment of annual accumulation of PD/T2 activity on MRI

Objective: To determine whether the efficacy of interferon beta-1b (IFN bet a-1b) on lesion activity could be shown with annual analysis of MRI. Backgr ound: Clinical outcomes and MRI burden of disease changes in MS patients in a multicenter double-blind placebo-controlled 5-year trial of IFN beta-1b have been reported, together with an analysis of 6-weekly MRI activity in a small subgroup during 2 years. MRI activity measurements based on annual s cans have not been documented. Methods: Patients were randomized into three treatment arms: placebo, 1.6 mIU, and 8 mIU IFN beta-1b self-administered subcutaneously every other day. Active lesions were identified as new, enla rging, or recurrent on proton density and T2-weighted MRI scans. Gadolinium was not used. An annual accumulation activity index was developed as an ad ditional analysis of lesion activity. Results: During the 5 years, both hig h- and low-dose IFN beta-1b groups showed a striking reduction in lesion an nual accumulation activity on the activity index versus placebo (p = 0.001) . Thirty-five percent of the high-dose patients and 29% of the low-dose pat ients were MRI inactive by this method of analysis, whereas only 16% of pla cebo patients were inactive (p = 0.001, placebo versus 8 mIU). Conclusions: This analysis of the annual accumulation of lesion activity shows that the previously reported treatment effect seen on MRI scanning once every 6 wee ks in a subcohort of the patients can also be seen on yearly scans. This an nual accumulation activity analysis provides an independent MRI confirmatio n of a treatment and dose effect for IFN beta-1b.