Résumé
Background and objectives: The therapeutic strategy in patients with late-onset MS (LOMS) remains poorly defined. In this study, we aimed to evaluate both clinical and MRI outcomes between 2 cohorts of patients with relapsing-remitting LOMS treated or not yet treated.Methods: Patients with relapsing-remitting MS were included for the analysis if disease onset occurred after 55 years and if they had at least one follow-up visit. The primary outcome was time to first relapse between 2 matched groups of patients with LOMS (treated and not yet treated). Secondary outcomes were as follows: (1) time to first confirmed disability progression (CDP), (2) time to first progression independent of relapse activity (PIRA) event, (3) time to secondary progression (SPMS), (4) time to first MRI activity, and (5) serious infection incidence rates (IIRs). For the comparative analyses, we adopted a time-dependent propensity score matching approach.Results: A total of 881 patients fulfilled the inclusion criteria. The mean (SD) age at onset was 59.9 (4.43) years. After applying propensity score matching, 436 patients were matched. The mean (SD) follow-up duration was 5.2 (4.27) years in the treated group and 5.0 (3.86) years in the not-yet-treated group. Mean (SD) time to first relapse was significantly longer in the treated group compared with the not-yet-treated group (7.0 years [0.33] vs 5.4 years [0.33]; p = 0.001). Mean (SD) time to first MRI activity was significantly longer in the treated group (5.9 years [0.33] vs 5.0 years [0.33]; p = 0.049). However, the mean time to CDP, PIRA, or SPMS was not different between the 2 groups (difference = 0.32 years; p = 0.585 for CDP; difference = 0.40 years; p = 0.442 for PIRA; difference = -0.02 years; p = 0.952 for SPMS). No increase in serious IIRs was observed with an incidence rate ratio of 0.38 (95% CI 0.07-2.10, p = 0.265) in the never-treated group compared with the treated one.Discussion: This study demonstrates a beneficial effect of disease-modifying therapy (DMT) on disease activity in patients with LOMS but without significant impact on disability progression. Main limitations are linked to the challenge of data collection and to the baseline imbalances between the 2 groups.Classification of evidence: This study provides Class III evidence that in patients with LOMS, treatment with DMTs is associated with a longer time to first relapse compared with those not treated with DMTs.