The F.D.A. usually follows advice from its advisory committees, and Alzheimer’s experts anticipated that the scans would be approved. The additional requirement would not be a big hurdle, said Dr. Daniel M. Skovronsky, chief executive of the company, Avid Radiopharmaceuticals, that applied to market the scans.
“We don’t know exactly what F.D.A. will want,” Dr. Skovronsky said. “But it should take months to generate this type of data, not years.”
The committee vote is “a very positive thing,” said Maria Carrillo, senior director of medical and scientific relations for the Alzheimer’s Association. “This is nothing but a positive for our families.”
More than five million Americans have Alzheimer’s disease.
Plaques are part of the criteria for having Alzheimer’s — if a person with memory problems does not have plaques, that person does not have Alzheimer’s. But without the scan, the only way to know if plaques were present is to do an autopsy.
Alzheimer’s specialists said they expected that if the scan were approved it would come into widespread use.
“This is a big deal,” said Dr. Pierre N. Tariot, director of the memory disorders center at the Banner Alzheimer’s Institute in Phoenix. Asked if he would be using the scans, Dr. Tariot replied, “Absolutely.”
Dr. Tariot is an investigator in studies by Avid, now a subsidiary of Eli Lilly & Company, and its competitors.
The approval would be for a dye that homes in on plaque in the brain, making it visible on PET scans. Such scans would be especially valuable in a common and troubling situation — trying to make a diagnosis when it is not clear whether a patient’s memory problems are a result of Alzheimer’s disease or something else. If a scan shows no plaque, the problems are not caused by Alzheimer’s and could be from tiny strokes or other diseases.
If a person has Alzheimer’s, though, there is as yet no treatment that can slow or reverse the disease, although new drugs are being tested that are intended to reduce plaque.
Nonetheless, doctors said, having a diagnosis is important for planning and for understanding what lies ahead. It also is important for family members to know because they are at increased risk if a mother or father, sister or brother has the disease. And people, they say, often want to know what is wrong with them, even when the news is bad.
The panel’s vote “has moved us a monumental step forward,” said Dr. Reisa Sperling, adding that with the scans “we will not just be guessing clinically.”
Dr. Sperling, director of the Center for Alzheimer’s Research and Treatment at
Brigham and Women’s Hospital in Boston, is an unpaid consultant to Avid Radiopharmaceuticals, which makes the dye, and said she paid her own way to speak at the F.D.A. meeting in White Oak, Md.
The question about interpreting the scans arose because in the Avid study, radiologists did not establish a firm cutoff point that would say whether a person had significant amounts of plaque. Instead they did a graded analysis. What is needed in practice is a set level that would say yes or no, and distinguish significant plaque accumulation from insignificant amounts. And the company must show that its cutoff points are accurate and that different radiologists assess the same scan in the same way.
Some people have plaque without having Alzheimer’s, so if a scan shows plaque, doctors will have to use their clinical judgment, taking into account a patient’s symptoms, in deciding what the scan results mean, noted Dr. P. Murali Doraiswamy, an Alzheimer’s researcher at
Duke University and a clinical investigator in the Avid trial. But if a scan shows no plaque, the situation is simpler, Dr. Doraiswamy said. It means the doctor should focus on other causes for the symptoms.
“This technique will allow family doctors to feel confident ruling out Alzheimer’s,” he said. “Until now we had to guess whether someone had plaques.”
In 2008, an advisory committee to the F.D.A. said that in order for the dye to be approved for amyloid imaging, the company would have to show that the scans were detecting the same plaques as were found on autopsy.
Avid did that, using people at the end of life who agreed to be scanned and then to have brain autopsies. The company also tested young healthy people who, presumably, would not have amyloid plaque in their brains. The scans found no plaque in those younger subjects.
At the meeting Thursday, a parade of medical experts testified about the need for the scans. Dr. Norman Foster, a professor of neurology at the
University of Utah, came at his own expense even though he is a consultant to GE Healthcare, which is developing its own brain scan for plaque, to urge approval of the Avid scan.
“Physicians currently have little confidence in their ability to determine the cause of
dementia, and as a result they often don’t even try,” Dr. Foster said. As a result, he said, families are left in limbo, unable to plan for the future if it is Alzheimer’s and, if it is not, delaying getting treatment.
“The preventable costs are enormous,” Dr. Foster said. “The emotional toll is incalculable.”
He told of three patients he had seen in the past two weeks who would have benefited from a scan. One is a 70-year-old man with memory problems and depression. He was given a diagnosis of depression, but only after he continued to get worse over two years did it become clear that he most likely had Alzheimer’s.
“I wish I had had the ability to do an amyloid PET scan to allow an earlier diagnosis,” Dr. Foster said. Approval of the scan, he said, “would be a historic advance in neurology and in the daily management of patients with memory complaints.”
With the committee’s vote, Dr. Doraiswamy said, “It’s a landmark day for our field.”
Bolivia, 3 de Diciembre de 2010. (Oficina de Información Pública OPS/OMS Bolivia) El dengue es una infección transmitida por mosquitos que en los últimos decenios se ha convertido en un importante problema de salud pública internacional. Se caracteriza por las diferentes presentaciones clínicas que van desde estados benignos hasta una evolución clínica grave y desenlaces que causan la muerte.
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