Effectiveness of early beta interferon on the first attack after confirmed multiple sclerosis: a comparative cohort study.

BACKGROUND: In the absence of randomized controlled trials to support therapeutic decisions in pediatric MS (multiple sclerosis), comparative observational studies based on the real practice of physicians are important tools. AIM: To assess the effectiveness of beta interferon (ssIFN) in preventing the first attack and severe disability after confirmed MS diagnosis in a pediatric cohort.
METHODS: A cohort of 197 relapsing-remitting pediatric MS patients was studied (1990-2005). Patients were followed from MS diagnosis until the first subsequent attack or severe disability occurrence (DSS score of >or=4) or were censored. The Cox model, with time-dependent ssIFN exposure to account for the varying times of starting this treatment, was used to estimate the effect of ssIFN on the risk of this attack or severe disability, adjusting for potential confounding factors.
RESULTS: During cohort follow-up (mean 5.5 years), 70.5% of the 197 children had a first attack (80% within the first 2 years) and 24 started ssIFN (mean delay 3.6 months; mean duration 17.1 months). The use of ssIFN was associated with a significant reduction in the rate of the first attack during the first year of treatment (hazard ratio: 0.31, 95% confidence interval: 0.13-0.72) as well as the first 2 years (0.40, 0.20-0.83). This effect was less significant over the entire follow-up of up to 4 years of treatment (0.57, 0.30-1.10). The use of ssIFN suggests a reduction on the occurrence of severe disability, although not statistically significant (HR 0.78; 95% CI: 0.25-2.42).
CONCLUSIONS: The use of ssIFN, given after the diagnosis of MS, significantly reduces the risk of relapse during the first 2 years.