Sustained disease remission after discontinuation of disease modifying treatments in relapsing-remitting multiple sclerosis.

Background: The natural history of multiple sclerosis (MS) following discontinuation of a first-line disease modifying treatment (DMT) in relapsing-remitting (RR-) MS patients is controversial, as few data are available on the risk of disease reactivation. This study aims to investigate the disease course after DMT discontinuation in selected RR-MS patients, exploring potential predictive factors of disease reactivation. Methods: RR-MS patients, aged 18-65, who had discontinued a first-line DMT were selected from 1107 clinical records. Relapses, disability worsening and new brain lesions, before and after DMT interruption, were retrospectively evaluated. Potentially predictive baseline characteristics of disease reactivation were also analysed. Results: N= 60 patients were included, median age and treatment duration were 47.8 (22.1-64.3) and 7.2 (0.5-17.8) years respectively. Median clinical follow-up after discontinuation was 4.6 (0.5-16.6) years. No disease rebound occurred. Mean annualized disease activity and relapse rate after discontinuation were both lower than during treatment(0.10±0.05 vs 0.15 ±0.05; p=0.017). A NEDA-3 period on treatment ≥5.5 years was associated with a low rate (7.7%) and a low risk of new disease activity (aHR 0.16, CI 0.03-0.78, p=0.024; Cox regression model multivariate analysis). The patients with NEDA-3 period threshold above 5.5 years showed a higher probability of surviving to disease reactivation than others (p=0.014). Conclusion: In most of the MS patients who showed a long NEDA-3 period while on treatment remission of disease activity persists following first-line DMT discontinuation, suggesting that prolonged suppression of disease activity on treatment can determine long term sustained remission of the disease also in absence of treatment.