Most disability accumulation in relapsing multiple sclerosis (MS) is not associated with overt relapses, challenging the current clinical distinction of relapsing and progressive forms of the disease, a new analysis shows. “We have to abandon the distinction between relapsing and progressive MS being different populations,” said lead author Ludwig Kappos, MD, University of Basel (Switzerland). “The disease appears to be more of a continuum of disability progression, which is sometimes also accompanied by relapses.”
The analysis was published online June 8 in JAMA Neurology.
Assessing disability progression
Noting that there are mounting data to suggest patients with relapsing MS frequently experience worsening disability over time – even when relapse activity appears well controlled – the researchers aimed to investigate the relative contributions of progression independent of relapse activity and relapse-associated worsening to overall accumulating disability in patients with relapsing multiple sclerosis. To do this, they analyzed data from two identical randomized clinical trials (OPERA I and OPERA II) conducted between 2011 and 2015, which compared treatment with the new B-cell–depleting therapy ocrelizumab with interferon beta-1a in 1,656 patients with relapsing MS.
Confirmed disability accumulation was defined by an increase in 1 or more of 3 measures (Expanded Disability Status Scale, timed 25-ft walk, or 9-hole peg test), confirmed after 3 or 6 months, and was classified as being related to a clinical relapse or occurring in the absence of a relapse.
Results showed that after 96 weeks (1.8 years) of treatment, 12-week composite confirmed disability accumulation had occurred in 29.6% of patients receiving interferon beta-1a and 21.1% of those given ocrelizumab; 24-week composite confirmed disability accumulation occurred in 22.7% of interferon beta-1a patients and 16.2% of the ocrelizumab group.
In both treatment groups, the vast majority of events contributing to disability accumulation occurred independently of relapse activity. In the interferon group, 78% of events contributing to 12-week confirmed disability accumulation and 80.6% of events contributing to 24-week confirmed disability accumulation occurred in the absence of clinical relapses, with the corresponding figures in the ocrelizumab group being 88.0% (12 weeks) and 89.1% (24 weeks).
Only a minority of patients (about 17% in both groups) had confirmed disability accumulation accompanied by clinical relapses. Very few patients with confirmed disability accumulation (4% to 5%) experienced disability worsening both associated and independent of relapses. Ocrelizumab was associated with a reduced risk of both relapse-associated and relapse-independent confirmed disability accumulation, compared with interferon beta-1a.
“We found that there was progression of disability in both groups, and the really astonishing finding was that although all patients were classified as having relapsing remitting MS, actually most of the disability progression occurred without preceding relapses,” Dr. Kappos commented. He noted that there have been two previous observational studies that have shown a high rate of disability progressions without temporal association to relapses in relapsing remitting patients, but this is the first time that this progression of disability independent of relapses has been shown in the controlled setting of two prospective, randomized clinical trials over a 2-year period.
“While we expected to see some disability progression independent of relapses, we were surprised to see that the disability progression occurring in both studies was almost exclusively happening without temporal relation to relapses. That was certainly an unexpected finding,” Dr. Kappos said. “These observations make it difficult to keep the current definitions of ‘relapsing remitting’ and ‘secondary progressive’ MS, [ones] that suggest a clear-cut distinction marked by the presence or absence of relapses. This can no longer be justified,” he stressed.
“We are not saying that relapses do not contribute to disability progression. There are a lot of data to support the fact that they do. But I think what we might be seeing is that the drug therapy is quite effective in reducing disability due to relapses but only partially effective in reducing progression independent of relapses,” Dr. Kappos explained.
Although there have been many advances in reducing relapses with drug therapy, focus now needs to shift to the other more continuous process of disability progression independent of relapses, Dr. Kappos said. “There is still a lot of room for improvement here.”
“If continuous progression independent of relapses is already present in the early phases of MS, it is reasonable to study the effects of intervention on steady progression already in this early phase,” he noted. “This might help to capture patients at earlier stages who better respond to treatment aimed at halting progression.”
Dr. Kappos also called for more subtle measurements of disability than the EDSS alone, including measures such as the 9-hole peg test and the 25-ft walk as they did in this analysis. But other measures could also be added that would characterize continuous disease activity and progression, such as laboratory values (e.g., neurofilament light chain) and advanced, more tissue-specific quantitative MRI techniques and digital biomarkers to detect subtle changes in neurologic function.
An artificial distinction?
Commenting on the study, Jeffrey Cohen, MD, director of the experimental therapeutics program at the Mellen Center for Multiple Sclerosis Treatment and Research, Cleveland Clinic, said he too sees very little distinction between relapsing remitting and progressive forms of the disease.
“This study confirms what has been suspected for quite a few years –that if one looks sufficiently and carefully, there is gradual worsening of some aspects of the disease in many patients from the earliest stages,” Dr. Cohen said. “Conversely, some patients with progressive MS have superimposed relapses or MRI lesion activity.
“Thus, the distinction between relapsing-remitting and progressive MS subtypes appears artificial,” he concluded.
This study was sponsored by F. Hoffmann–La Roche. Dr. Kappos has received research support from the company.
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