A negative scan, says Weiner, could be reassuring. "Let's say I have a person that's having quite a bit of memory problems, but the scan is negative. Well, that's good news. That's very good news. They are very unlikely to show a rapid deterioration from Alzheimer's."
The new tracer scans "should not be used in everybody," says James E. Galvin, M.D., director of the Pearl Barlow Center for Memory Evaluation and Treatment at New York University's Langone Medical Center. He says if the patient has symptoms consistent with Alzheimer's and the doctor is confident of the diagnosis, the scan would add little information.
Its utility, he believes, will be in helping to resolve "diagnostic dilemmas" where symptoms and other findings leave significant room for doubt. And in tracking the effects of experimental drugs.
One more tool to help with a cure
Finding Alzheimer’s early is critical both to discovering treatments that attack the disease—currently there are none—and not just its symptoms. Researchers believe the damage in the brain begins a decade or more before an individual notices symptoms. Indeed, it may be that many experimental drugs have failed to arrest or even slow Alzheimer’s because they came too late; dead brain cells don’t come back to life.
The new amyloid tracer (florbetapir F18) represents only one of several recent advances in techniques for observing Alzheimer’s disease in the brain, says Maria C. Carrillo, senior director for medical and scientific relations for the Alzheimer’s Association, host of the conference in Honolulu. “What’s exciting about our current state of knowledge,” she says, “is that we now understand that early detection is possible. That gives us so much hope.”
Other tests that measure signs of Alzheimer’s—from key proteins in spinal fluid to other kinds of imaging—seem to offer a telling glimpse into the disease at different points along its destructive path through the brain. Each may prove a useful source of information at different stages of Alzheimer’s.
The new tracer builds on scientific pioneering by University of Pittsburgh researchers who developed an agent that helped spotlight plaque in the brain. But their compound has a very short life and can only be used by high-tech research centers. Use by doctors in hospitals and clinics is out of the question.
Avid’s new tracer, on the other hand, lasts long enough to allow its transport from manufacturing sites to scanning clinics, potentially reaching about 90 percent of the country, says company spokesperson Christopher Bunting.
Will it be covered by insurance?
For these new brain scans to enter widespread use, both experts and insurers will need to be convinced that they provide some clear benefit—making it easier for patients to get treatment, for example.
Currently the standard evaluation for possible Alzheimer’s disease includes some type of brain imaging—a CT (computed tomography) or MRI—mostly to rule out other problems such as a stroke or tumor.
The more specialized PET test is used far less often, and is covered by Medicare only for the specific purpose of distinguishing Alzheimer’s from a relatively rare condition called fronto-temporal dementia, which typically produces quite different findings on the scan.