By Eleanor McDermid, Senior medwireNews Reporter
Patients with amyotrophic lateral sclerosis (ALS) often have periods of stable disease, with some even experiencing brief improvements, shows analysis of the PRO-ACT database.
The researchers found that 25% of the 3132 participants with 6 months of follow-up did not decline on the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS). The proportion was lower among 2105 patients monitored for 12 months, at 16%, but even over 18 months of follow-up, 7% of 1218 patients remained stable.
“In light of this information, responder analyses that interpret stable disease over short intervals as evidence of treatment benefit must be met with skepticism”, observe Richard Bedlack (Durham VA Medical Center, North Carolina, USA) and colleagues.
The team also identified periods of improved disease among 14% of 1343 patients with at least four measurements on the revised ALSFRS over at least one 180-day period. These reversals were “not uncommon”, with some being caused by a single revised ALSFRS score that was a significant improvement on previous measurements.
“These may indicate a measurement error, or the effect of a symptomatic treatment”, write the researchers in Neurology.
More sustained reversals – of at least 4 points on the revised ALSFRS lasting 12 months or longer – were “more interesting”, but rare, occurring in less than 1% of patients, say Bedlack et al.
“These may suggest an ALS mimic syndrome, an endogenous mechanism that is able to compensate for the disease, a deleterious exogenous environmental influence that was removed, or even an undocumented treatment that is working”, says the team.
At the time of the study, PRO-ACT contained data from 17 studies, most of which were clinical trials. However, reversals occurred with similar frequency when the analysis was restricted to placebo-treated patients, suggesting that they were not a previously undetected effect of active treatment.
The group of patients with reversals contained a significantly increased proportion of men and appeared to have more slowly progressing disease than the group without reversals, although the researchers say “it is difficult to know how much importance to ascribe to these findings.”
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