FDA Panel Recommends Brain Imaging Agent to Help Diagnose PD, Dementia with Lewy Bodies

Barbara Boughton

August 17, 2009

August 17, 2009 — An experimental GE Healthcare imaging agent called DaTSCAN that can detect loss of dopaminergic neurons — seen in diseases such as Parkinson's disease (PD) and dementia with Lewy bodies — has a favorable risk/benefit profile, according to a US Food and Drug Administration (FDA) advisory committee.

The panel voted 11 to 2 in favor of the agent and said it could be a useful adjunctive diagnostic tool for clinicians in evaluating patients. There was one abstention.

GE Healthcare is seeking FDA approval for its radiopharmaceutical imaging agent to be used along with single photon emission computed tomography imaging. DaTSCAN images are abnormal in patients with PD and dementia with Lewy bodies but normal in patients without dopaminergic neurodegeneration, such as those with essential tremor and Alzheimer's disease.

The FDA will consider the advisory committee's recommendations and is expected to make a decision on the drug's approval by early September.

Aid for Differential Diagnosis?

"This might make a real difference in 5% of patients seen by movement disorders specialists and 15% of patients seen by general practitioners, and that's an important number of patients," committee member Nathan Fountain, MD, associate professor of neurology at the University of Virginia, Charlottesville, told Medscape Neurology. Dr. Fountain voted in favor of the agent.

"There are many circumstances I can think of and imagine where this could be a benefit, and the risks are very low," said Karl Kierburtz, MD, MPH, committee member and professor of neurology and community and preventive medicine at the University of Rochester, New York.

Dr. Kierburtz noted that there are many instances where DaTSCAN could help improve the diagnostic accuracy of clinicians and decrease some of the problems associated with other means of differential diagnoses — such as medication challenges, which often work poorly in the elderly or patients with dementia.

However, although the committee members pointed out the benefits of the agent, they also voiced concerns about how it might be used. "I have reservations about how widely and in what clinical situations it might be used. I'd be concerned that if it was widely available, it could be used if there is even a suspicion of a movement disorder," said committee member Peter Herscovitch, MD, from the National Institutes of Health Clinical Center, Bethesda, Maryland.

The committee members emphasized that DaTSCAN was not suitable for screening or prognosis on its own. "We don't want to make this the gold standard for diagnosing [PD]. This should not be the comparator," added Dr. Gregory Holmes, MD, professor of medicine at Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, who also voted in favor of the agent.

Efficacy and Safety Concerns

Those who voted against DaTSCAN did so because of safety concerns and doubts that GE Healthcare had proven the drug's clinical utility. Wilson DeCamp, PhD, the patient representative on the committee, voiced concerns that there had been 5 deaths in 8 completed clinical studies on the drug.

Company representatives responded that the deaths were unrelated to the agent, but Dr. DeCamp pointed out that DaTSCAN had been used in over 200,000 patients since it was approved for marketing in Europe in 2000, and "the risk to patients may have been underestimated," he said.

Dr. Stacy Rudnicki, MD, who also voted against the agent, voiced concerns that it had not been proven to be an aid in clinical management of patients with PD or dementia. She also noted that the question of whether DaTSCAN could influence outcomes was largely unanswered. Dr. Rudnicki is professor of neurology at the University of Arkansas, Little Rock.

In a presentation before the committee, Joel Perlmutter, MD, professor of neurology at Washington University School of Medicine, St. Louis, Missouri, said that after reviewing the scientific literature, he did not think that DaTSCAN was cost-effective.

He highlighted difference in cost between DaTSCAN ($1500 per scan) versus a month's trial of carbidopa or levodopa for a patient with possible PD ($150). "I don't think the data is sufficiently compelling and the cost/benefit is marginal," he said. "It wouldn't change how I would treat a patient."

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