Minimal evidence of disease activity (MEDA) in relapsing-remitting multiple sclerosis.

Abstract

This study aimed to define the minimal evidence of disease activity (MEDA) during treatment that can be tolerated without exposing patients with relapsing-remitting multiple sclerosis at risk of long-term disability. We retrospectively collected data of patients followed up to 10 years after starting interferon beta or glatiramer acetate. Survival analyses explored the association between the long-term risk of reaching an Expanded Disability Status Scale≥6.0 and early clinical and MRI activity assessed after the first and second year of treatment. Early disease activity was classified by the so-called 'MAGNIMS score' (<i>low</i>: no relapses and <3 new T2 lesions; <i>medium</i>: no relapses and ≥3 new T2 lesions or 1 relapse and 0-2 new T2 lesions; <i>high</i>: 1 relapse and ≥3 new T2 lesions or ≥2 relapses) and the absence or presence of contrast-enhancing lesions (CELs). At follow-up, 148/1036 (14.3%) patients reached the outcome: 61/685 (8.9%) with <i>low</i> score (reference category), 57/241 (23.7%) with <i>medium</i> score (HR=1.94, p=0.002) and 30/110 (27.3%) with <i>high</i> score (HR=2.47, p<0.001) after the first year of treatment. In the <i>low</i> score subgroup, the risk was further reduced in the absence (49/607, 8.1%) than in the presence of CELs (12/78, 15.4%; HR=2.11, p=0.01). No evident disease activity and <i>low</i> score in the absence of CELs shared the same risk (p=0.54). Similar findings were obtained even after the second year of treatment. Early marginal MRI activity of one to two new T2 lesions, in the absence of both relapses and CELs, is associated with a minor risk of future disability, thus representing a simple and valuable definition for MEDA.