Objective: To investigate the effect of disease-modifying treatment on short-term disability outcomes in secondary progressive multiple sclerosis (SPMS).
Methods: Using MSBase, an international cohort study, we previously validated a highly accurate definition of SPMS. Here, we identified patients in MSBase who were either untreated or treated with a disease-modifying drug when meeting this definition. Propensity score matching was used to select subpopulations with comparable baseline characteristics. Disability outcomes were compared in paired, pairwise-censored analyses adjusted for treatment persistence, visit density, and relapse rates.
Results: Of the 2,381 included patients, 1,378 patients were matchable (treated n=689, untreated n=689). Median pairwise-censored follow-up was 2.1 years (quartiles 1.2-3.8 years). No difference in the risk of 6-month sustained disability progression was observed between the groups (hazard ratio [HR] 0.9, 95% confidence interval [CI] 0.7-1.1, p=0.27). We also did not find differences in any of the secondary endpoints: risk of reaching Expanded Disability Status Scale (EDSS) score $ 7 (HR 0.6, 95% CI 0.4-1.1, p=0.10), sustained disability reduction (HR 1.0, 95% CI 0.8-1.3, p=0.79), or change in disability burden (area under the EDSS-time curve, beta=20.05, p=0.09). Secondary and sensitivity analyses confirmed the results.
Conclusions: Our pooled analysis of the currently available disease-modifying agents used after conversion to SPMS suggests that, on average, these therapies have no substantial effect on relapse-unrelated disability outcomes measured by the EDSS up to 4 years.
Classification of evidence: This study provides Class IV evidence that for patients with SPMS, disease-modifying treatment has no beneficial effect on short-term disability progression.