Compared with the natural history of the disease, disease-modifying treatments for multiple sclerosis (MS) significantly reduce the risks of long-term disability worsening and evolution to secondary progressive MS (SPMS), according to research published in the October issue of Annals of Neurology. The data also suggest that patients who have no evidence of disease activity (NEDA) for two years are no more likely to have long-term stability than patients who do not reach this end point.
“These observations challenge the concept that NEDA represents remission. Although NEDA may be a useful measure for assessing relative therapeutic efficacy, many patients who meet NEDA criteria over two years go on to develop clinically significant disability,” said Bruce A. C. Cree, MD, PhD, Associate Professor of Neurology at the University of California, San Francisco School of Medicine. “Worsening in patients who meet the two-year NEDA end point could result from active spinal cord disease not captured with brain MRI, progressive axonal or neuronal degeneration, or an escape from a true but transient remission state.
Bruce A. C. Cree, MD, PhD
Researchers had anticipated that between 36% and 50% of patients with relapsing MS (RMS) would develop SPMS, but 11.3% of the cohort transitioned to SPMS during the course of the study. Evolution of sustained disability was also slower than expected, said Dr. Cree.
Examining Long-Term Effects of Treatment
Natural history studies from the pretreatment era suggest that between one-third and one-half of patients with MS experience substantial worsening of neurologic disability approximately 15 years after disease onset. Disease-modifying therapies in MS have been studied during the past two decades and are associated with improvement in the short term. Their effect on long-term outcomes is unknown, however. Furthermore, little is known about the relationship between short-term MRI measurements and long-term disability in MS.
As a result, Dr. Cree and colleagues conducted a prospective study to characterize the accrual of long-term disability in a cohort of actively treated patients with MS. Additionally, they sought to assess whether clinical and MRI data used in clinical trials have long-term prognostic value.
Eligible participants had all clinical subtypes of MS and were first evaluated at the MS Center at the University of California, San Francisco between July 2004 and September 2005. Patients were excluded if they were unable to tolerate MRI scans, had poor venous access, or if they had other significant medical illnesses that might interfere with goals of the study. Investigators followed participants annually for five years. In addition, patients underwent re-evaluation at extended time points for as long as 10 years after baseline.
Researchers defined disability progression as a clinically significant worsening in the Expanded Disability Status Scale (EDSS), the timed 25-foot walk, the nine-hole peg test, and the paced serial auditory addition test.
Two Tiers of Therapy
Participants were treated with FDA-approved therapies or off-label therapies. Researchers defined two treatment tiers and categorized therapies based on their relative perceived effectiveness using data from clinical trials.
The first tier of treatment, platform therapy, included interferon (IFN) beta, glatiramer acetate, and off-label therapies such as glucocorticoids, azathioprine, and mycophenolate mofetil. The second tier of treatment, high-potency therapy, included natalizumab, rituximab, mitoxantrone, and cyclophosphamide.
NEDA and Long-Term Disability
Of 517 actively managed patients with MS enrolled in the study, 366 had RMS, 48 had SPMS, 21 had primary progressive MS (PPMS), and 82 had clinically isolated syndrome (CIS). After 10 years of follow-up, neurologic disability was stable or improved, compared with baseline, in 41% of patients. Serum vitamin D levels were inversely associated with short-term MS disease activity, but were not associated with long-term disability. At a median time of 16.8 years after disease onset, 10.7% of patients reached an EDSS score of greater than or equal to 6, and 18.1% of patients evolved from RMS to SPMS.
The investigators concluded that evolution to SPMS in this study was significantly lower than expected, based on natural history studies. They also noted that short-term increases in EDSS did not necessarily predict future accumulation of long-term disability in patients with RMS. In addition, subjects with NEDA by clinical and MRI criteria during the first two years had long-term outcomes that were no different from those of the cohort as a whole.
“Treating to target with two-year NEDA as the goal may not result in protection against long-term disability,” said Dr. Cree. “Long-term studies are urgently needed to determine if high-intensity therapy, initiated at the time of diagnosis or used in patients with seemingly inactive disease, is superior to the escalation approach employed in this cohort.”
—Erica Tricarico
Suggested Reading
University of California, San Francisco MS-EPIC Team, Cree BA, Gourraud PA, et al. Long-term evolution of multiple sclerosis disability in the treatment era. Ann Neurol. 2016;80(4):499-510.