Rate of brain atrophy in relapsing MS decreases during treatment with IFNβ-1a

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Abstract
Objective: To determine the time course of brain atrophy during treatment with once-weekly IM interferon β-1a (IFNβ-1a). Methods: The MRI cohort (n = 386) of the European IFNβ-1a dose comparison study in relapsing multiple sclerosis (MS) was analyzed. In addition to baseline and three annual scans, a frequent subgroup (n = 138) had two scans before treatment initiation and scans at months 4, 5, 6, 10, and 11. Brain parenchymal fraction (BPF), a normalized measure of whole-brain atrophy, and volume of Gd-enhancing lesions (T1Gd) and T2 hyperintense lesions (T2LL) were evaluated. Results: BPF decrease was −0.686% (first year), −0.377% (second year), and −0.378% (third year). Analysis of the frequent subgroup showed that 68% of the first-year BPF decrease occurred during the first 4 months of treatment. This change was paralleled by a drop in T1Gd and T2LL. In the frequent subgroup, an annualized atrophy rate was determined by a regression slope for the pretreatment period and from month 4 of treatment onward. Annualized pretreatment rate (−1.06%) was significantly higher than the under-treatment rate (−0.33%). Conclusions: In the first year of treatment with anti-inflammatory agents, atrophy measurements are possibly confounded by resolution of inflammatory edema or more remote effects of previous damage to the CNS. The atrophy rate reduction observed after treatment month 4 may reflect a beneficial but partial effect of interferon β-1a and was sustained over the 3-year study period.