Natural history of relapsing remitting multiple sclerosis in a long-lasting cohort from a tertiary MS centre in Portugal

Background: Several disease-modifying therapies (DMTs) have emerged in the last two decades for the treatment of multiple sclerosis (MS). The increasing use of these therapies has enhanced the need to study its impact on long-term disease progression and on the natural history of MS. This study aimed to characterize a Portuguese MS patient cohort in what concerns the natural history of disease by exploring differences throughout 3 decades. Methods: Longitudinal, retrospective, non-interventional study. Patients aged >= 18 years old, with confirmed diagnosis of relapsing-remitting MS (RRMS), were included. Biodemographic and clinical characteristics (MS diagnosis, patient follow-up, relapses, treatment, and exams) were assessed and compared according to the first appointment date throughout 10-year spans (1987-1996; 1997-2006; 2007-2016). Results: 548 patients were included in this analysis. Significant differences were observed between decades for evoked potential (EP) and cerebrospinal fluid (CSF) exams conducted at diagnosis, the first with less expression on the last decade; the median number of relapses per year (higher in the subgroup 07-16); EDSS at baseline and at last appointment (both higher in the subgroup 87-96); and the percentage of patients achieving EDSS 3.0 and EDSS 6.0 (increased in the subgroup 87-96). Additionally, time from diagnosis to first treatment was significantly lower in patients from the most recent decade, and a greater percentage of such patients, compared to the other two subgroups, was, at last appointment, under a second line DMT. Conclusion: In general, our study reflects findings from longitudinal studies on MS progression already published in the literature. In recent years, the growing number of more effective DMTs, along with earlier disease detection, and improvements in access to healthcare appear to have had a positive impact on patients' access to treatment and, consequently, disease progression. Additional studies, with increased follow up time, are needed to further investigate the effect of treatment improvement in the natural history of MS.