Magnetic resonance imaging predictors of conversion to multiple sclerosis in the BENEFIT study

BACKGROUND: Several studies have confirmed the predictive value of baseline and follow-up magnetic resonance (MR) imaging variables for conversion to clinically definite multiple sclerosis (CDMS), depending on the population, follow-up duration, and treatment intervention. However, the timing of follow-up imaging and the effect of treatment intervention on the predictive value of baseline MR imaging variables require further elucidation. OBJECTIVES: To assess the prognostic value of baseline MR imaging variables for conversion to CDMS over 3 years and whether this was affected by treatment intervention and (2) to assess the increased risk for conversion posed by dissemination in time on follow-up MR imaging. DESIGN: Cohort study. SETTING: Multicenter randomized clinical trial. PATIENTS: Four hundred sixty-eight patients with a clinically isolated syndrome who had an initial clinical demyelinating event within the past 60 days who received early treatment (3 years of interferon beta-1b) or delayed treatment (placebo first, followed by < or =1 year of interferon beta-1b). Intervention Magnetic resonance imaging. Main Outcome Measure Time to CDMS. RESULTS: The overall conversion rate to CDMS was 42%. Barkhof criteria with the strongest prognostic value were the presence at baseline of at least 9 T2-weighted lesions (hazard ratio [HR], 1.64; 95% confidence interval [CI], 1.15-2.33; P = .006) and at least 3 periventricular lesions (1.66; 1.14-2.41; P = .009). No specific advantage was noted in using a fixed cutoff of at least 3 Barkhof criteria (HR, 1.31; 95% CI, 0.95-1.79; P = .10). The prognostic value of all MR imaging criteria was unaffected by treatment intervention (P < or = .20 for all). Dissemination in time resulted in increased risk for CDMS only in patients without dissemination in space at baseline and was most informative at the 9-month MR imaging (HR, 2.72; 95% CI, 1.26-5.87; P = .01). CONCLUSIONS: The modified Barkhof criteria showed moderate predictive value for conversion to CDMS, although all patients had received interferon beta-1b therapy for at least 1 year. The predictive value was unaffected by treatment intervention. Follow-up MR imaging was most informative after 9 months in patients without dissemination in space at baseline.