Initial relapsing phase hastens postprogression MS disability
medwireNews: Patients in the progressive phase of multiple sclerosis (MS) have a faster decline towards disability if they previously had a clinical relapsing phase, say researchers.
Furthermore, the rate at which patients reached an Expanded Disability Status Scale (EDSS) score of 6 was further accelerated if they had postprogression relapses, independently of the effects of preprogression relapses.
Progression accounts for most disability accrual in MS, say Orhun Kantarci (Mayo Clinic College of Medicine, Rochester, Minnesota, USA) and study co-authors. However, given their findings, they suggest that some patients may benefit from continued therapy to prevent relapses after progression onset.
They found that just 3.1% of the 322 patients with primary progressive MS (PPMS) had relapses, as did 10.7% of the 112 patients with single-attack progressive MS. By contrast, 29.5% of the 421 patients with secondary progressive MS (SPMS) had relapses after the onset of progression.
Nearly all (95.2%) of these postprogression relapses occurred in patients younger than 55 years and 91.6% occurred within 5 years of patients entering the progression phase. Thus, “a logical extension is that intervention to prevent postprogression relapses would be most effective in this period”, say the researchers, particularly in patients with bout-onset progressive MS.
Postprogression relapses shortened the time to reach an EDSS score of 6 by about 2 years. The overall time was shortest in patients with SPMS, longest in those with PPMS and intermediate in those with single-attack progressive MS, with 50% of patients reaching this marker within 4, 10 and 7 years, respectively.
The team believes that the differences may reflect both clinical relapse-related and relapse-independent mechanisms. At onset of progression, the average EDSS score was less than 2 points higher in SPMS than PPMS patients, at 3.4 versus 1.5–2.0, and average pyramidal functional system scores were similar between the groups, indicating that disability caused by preprogression relapses had only a small effect on the postprogression disability accrual.
“It is also possible that a relapsing course preceding progressive disease onset reflects higher subclinical activity ([magnetic resonance imaging] lesion accumulation) in these patients”, Kantarci et al write in Neurology.
Older age was associated with a shorter time to EDSS 6, as was female gender. The latter finding “seemingly contradicts long-held views of prognosis in MS”, say the researchers, “namely, male sex imparts a worse prognosis.”
However, they point out that this is based on men being more likely than women to develop progressive disease, whereas the current study only included patients who were already in the progressive phase.
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By Eleanor McDermid, Senior medwireNews Reporter