LONDON — Using two different novel high-affinity radiotracers with positron emission tomography (PET), investigators were able to detect microglial activation in white matter lesions in patients with multiple sclerosis (MS) across all disease stages, they reported here September 15 at the Congress of the European Committee on Treatment and Research in Multiple Sclerosis.
“For the first time, we have directly evaluated comparable cohorts with two novel PET tracers using identical analyses and shown consistent results,” said Gourab Datta, MD, a clinical research fellow at Imperial College London, in presenting the findings. “We found a wide heterogeneity of inflammatory activity among lesions, consistent with neuropathological studies. Active inflammatory lesions were detected across disease stages and treatments.”
The small study included 36 MS patients and 33 healthy controls.
The radiotracers, or ligands — (11C)PBR28 and (18F)PBR111 — showed microglial activation in patients with early and late disease, as well as those being treated with interferons and the newer disease-modifying agents such as fingolimod, nataluzimab, and alemtuzumab.
“Gadolinium enhancement identifies only a small proportion of lesions with inflammatory activity,” said Dr. Datta. “But the use of these PET radiotracers made it possible to identify four different lesion classifications — active, peripherally active, inactive, and undifferentiated — at different stages of disease.
Dr. Datta said that about 30 percent of patients who had been diagnosed with MS for one to seven years showed either active or peripherally active disease using the new ligands; about 25 percent of the patients who had been diagnosed for eight to 11 years showed signs of activity, as did 30 percent of those who had MS for 12 to 16 years and about 35 percent of those with MS for 17 to 28 years.
Although about 35 percent of the patients with progressive MS showed no activity, Dr. Datta said that the imaging scans did reveal that another 25 percent had lesions described as active and 5 percent had peripherally active lesions.
In the patients diagnosed with relapsing-remitting multiple sclerosis, about 22 percent had inactive disease, but 18 percent had active lesion and another 7 percent had peripherally active lesions, he reported.
Treatment didn't necessarily quell the disease activity either, Dr. Datta noted. About 10 percent of relapsing-remitting MS patients who were not under treatment had no signs of disease activity, but about 15 percent had signs of activity or peripheral activity. The most prevalent lesions seen — about 70 percent of the total — were described as undifferentiated.
“We have to integrate a lot of pieces in order to get a full picture of multiple sclerosis activity,” said Daniel Reich, MD, PhD, senior investigator at the National Institute of Neurological Disorders and Stroke, who was not involved with the study. “This is but one piece of the puzzle.
“I don't think we can say anything definitive about this,” he told the Neurology Today Conference Reporter. “This is a 30-person study with a new technology.”
Dr. Reich, who was the co-moderator of the session, added, “This is an area which needs further exploration.”
Neurology Today Conference Reporters, sent out in email blasts, report brief highlights from professional meetings throughout the year. In September, the Neurology Today Conference Reporter reported onsite from the 2016 Congress of the European Committee on Research and Treatment of Multiple Sclerosis (ECTRIMS) that appeared online in September. Look for expanded discussion of these reports in an upcoming print edition of Neurology Today. For more briefs from the meeting, go to http://bit.ly/NT-ECTRIMS.
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