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We compared the number of new gadolinium-enhancing and T2-weighted lesions on six monthly MRI scans in eight patients with relapsing multiple sclerosis before and during treatment with weekly intramuscular interferon beta-1a (Avonex; 30 microg). MRI activity was modestly reduced during treatment (p = 0.016). The treatment effect was also significant after adjusting pretreatment lesion frequency for regression to the mean. Based on this pilot study, Avonex, as approved for treatment of relapsing forms of MS in the United States, reduces new MRI activity.

We compared the number of new gadolinium-enhancing (Gd+) and T2-weighted (T2W) lesions on 6-monthly MRI scans before and after initiating weekly intramuscular injections of interferon beta-1a (Avonex) 30 mcg. The mean number of new focal Gd+ lesions detected during the 6 monthly on-treatment scanning sessions was 58 per cent less per MRI scan and 62.5 per cent less per patient than during the 6 monthly pre-treatment scanning sessions (p = 0.016, Wilcoxon signed rank test). The results are similar for new focal Gd+ and T2W lesions. The reduction in disease activity detected by monthly Gd+ enhanced MRI scans after initiating weekly intramuscular interferon beta-1a 30 mcg is consistent with benefits observed with thrice weekly subcutaneous interferon beta-1a 10 and 30 mcg and alternate day subcutaneous interferon beta-1b 8.0 MIU.