Determinants of MS re-activation after discontinuing therapies.

Introduction: A decision to discontinue MS immunotherapies is common in clinical practice - whether in order to switch to another therapy or at an advanced stage of progressive MS without relapses. The evidence regarding individual risk of MS re-activation after treatment discontinuation is limited. Aim(s): To evaluate associations of demographic and clinical patient characteristics with the risk of relapses after discontinuing treatment. Both overall and treatment-specific associations are explored. Method(s): Using the global MSBase registry, we identified all patients who discontinued MS immunotherapy after >=3 months on treatment, with the recorded disability score (EDSS) at the time of discontinuing treatment, and prospectively recorded follow-up of >=6 months. The probability of experiencing a relapse after discontinuing treatment, conditional on patient characteristics, was analysed with Cox proportional hazards model. Differences in these associations among different therapies were studied with interaction terms. Result(s): 24,989 episodes of treatment discontinuation were recorded from 17,871 patients (74% female, mean age at discontinuation 39 years, 88% relapsing-remitting MS, mean MS duration 10 years, median EDSS 2.5). The patient characteristics associated with a lower hazard of MS re-activation were male sex (b=0.87, p< 0.001), older age (b=0.98, p< 0.001), MS duration (b=1.01, p< 0.001), secondary progressive MS (b=0.73, p< 0.001), longer treatment duration (0.95, p< 0.001), greater number of prior treatments (1: b=0.62, p< 0.001; >=2: b=0.39, p< 0.001) and greater number of relapses during the previous year (1: b=1.30, p< 0.001; >=2: b=1.62, p< 0.001). The characteristics associated with a greater risk of MS re-activation were clinically isolated syndrome (b=1.87, p< 0.001) and greater EDSS (4-5.5: b=1.41, p< 0.001; >=6: b=1.17, p=0.001). Therapies used more recently (dimethyl fumarate, fingolimod, natalizumab) tended to be associated with a lower h