Objective: The objective of this paper is to investigate four-year outcomes of interferon beta (IFNB)-treated patients with multiple sclerosis (MS) according to their clinical or magnetic resonance imaging (MRI) activity status at first year of treatment.
Methods: A total of 370 patients with MS duration ≤5 years before IFNB start were followed-up for four years. The optimal threshold for one-year MRI activity that more accurately predicted subsequent relapses or disability worsening was identified. The risk of relapses and disability worsening after the first year was then estimated by propensity score (PS)-adjusted analyses in patients fulfilling European Medicines Agency (EMA) criteria for second-line escalation and in those with isolated MRI activity.
Results: A total of 192 (51.9%) patients relapsed, and 66 (17.8%) worsened in disability from year 1 to 4 of follow-up. The more accurate threshold for one-year MRI activity was the occurrence of ≥1 enhancing or ≥2 new T2-lesions. An increased risk of relapses and disability worsening was found in either patients fulfilling EMA criteria (hazard ratio (HR) = 3.69, and HR = 6.02) and in those experiencing isolated MRI activity (HR = 3.15, and HR = 5.31) at first year of treatment, when compared with stable patients (all p values <0.001).
Conclusion: The four-year outcomes of patients with isolated MRI activity did not differ from those fulfilling EMA criteria at first year of IFNB treatment.
Keywords: Multiple sclerosis; breakthrough disease; interferon beta; observational study; propensity score; therapeutic algorithm.