Several retrospective studies have demonstrated the clinical benefits of immunosuppressive therapies (IST) such as azathioprine (AZA), mycophenolate mofetil (MMF) and rituximab (RTX) for reducing relapse rates in neuromyelitis optica spectrum disorders (NMOSD) patients. However, there is considerable uncertainty regarding the relative benefits and harms associated with each of these IST in real world clinical practice and current data describing the strategies are limited
The objective of this study was to describe the incidence of relapses in patients with NMOSD under IST included in the Argentinean MS and NMOSD registry (RelevarEM, NCT 03375177).
We conducted a retrospective cohort study from RelevarEM. RelevarEM is a longitudinal, strictly observational MS and NMOSD registry in Argentina. From May 2018 to June 2020, the centers and principal investigators were contacted, and patients were incorporated into the Registry. NMOSD patients were defined based on the 2015 International Consensus Diagnostic Criteria for NMOSD. Relapses during the study period, demographics and radiological (e.g. new/enlarging and/or enhancing-contrast MRI lesions) data were collected. Only patients under IST were included in the analysis. Patients contributed person-years of follow-up for the study period. Incidence rates and 95% CI were calculated. Thus, global and associated with each IST incidence density rate of relapses was estimated.
We included a total of 132 (77% women) NMOSD patients with a median age at diagnosis of 36 years (27-47) and a disease duration of 6 years (4-10). Aquaporin-4 antibody was positive in 54.8%. At the time of entering the registry, 39.4% were treated with RTX, 33.3% with AZA, 3.6% MMF. The global incidence density rate of relapse was 0.032/person-year (CI95% 0,021-0,048), for RTX 0.051 (CI95% 0,024-0,1) and for AZA 0,031 (CI95% 0,016-0,06). There were no relapses in the group of MMF during this period of time.
This study showed a low incidence density rate of relapses in NMOSD patients under IST during this study period. Further studies will help expand our initial findings, hopefully leading to improve treatment options for NMOSD patients.