Progression Independent of Relapsing Biology in Multiple Sclerosis: A Real World Study
Heather Yong1, Carlos Camara Lemarroy2
1Alberta Health Services, 2Neurology, University of Calgary Department of Neurology, Alberta Health Services
Objective:
Herein we aimed to determine the existence of progression independent of relapse activity (PIRA) in a real-world cohort of people with relapsing-remitting multiple sclerosis (RRMS), using a more stringent criterion defined as Progression Independent of Relapse Biology (PIRB).
Background:
PIRA implies the existence of disability accumulation (DA) in people with RRMS independent of relapses. This has the potential to lead to a paradigm shift involving the traditional distinction between progressive and RRMS.
Design/Methods:
Participants were drawn from the observational Clinical Impact of Multiple Sclerosis study, carried out in the University of Calgary MS clinic of RRMS patients on fingolimod or ocrelizumab. PIRB was defined as DA from baseline to the end of study observation, and absolute exclusion of relapses, inflammatory MRI activity, interim worsening in disability with subsequent improvement, and progression secondary to alternative causes such as formal conversion to secondary-progressive MS. PIRB in a clinical trial cohort was also determined with data from the Minocycline phase III trial of a first demyelinating MS event (MinoCIS, NCT00666887).
Results:
In the ocrelizumab (n=296) and fingolimod (n=245) groups, 14.86% (n=44) and 30.20% (n=74) of RRMS participants experienced DA at (3.36–5.27 years) of follow-up respectively. In the MinoCIS group (n=142) twenty participants (14.1%) experienced DA at 24 months. Of those who amassed disability, only a small proportion displayed PIRB (3.67%, 3.72%, 3.52%) in the fingolimod, ocrelizumab, and minocycline groups respectively. The most common causes of DA were transition to secondary-progressive MS, and new MRI activity.
Conclusions:
Compared to PIRA, PIRB is rare and occurs at a consistent rate across all cohorts studied (both in the real-world and in clinical trials) despite varied rates of participant progression. We suggest that disability in RRMS is predominantly driven by MRI/clinical relapse and transition to the biologically distinct secondary-progressive MS, with only a small proportion of RRMS patients experiencing PIRB.
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