Study to Examine Amyloid PET Scans as Diagnostic Tool for Alzheimer’s

A hallmark feature of Alzheimer’s disease is the build-up of fibrous plaques of a protein fragment called amyloid-beta. Historically, these plaques could be identified only postmortem, but recent advances in imaging are now enabling clinicians to view these amyloid plaques in living people.

One big hurdle, however, is that while amyloid plaques are a key component of Alzheimer’s, the relationship between these structures, disease progression, and disease severity remains murky. (For example, after showing some initial promise, antibodies designed to destroy amyloid plaques have shown less than stellar results in several clinical trials.)

Given that positron emission tomography (PET) scanning of the brain is costly, the Centers for Medicare and Medicaid Services (CMS) ruled in 2013 that there was insufficient evidence that such scanning would be necessary in the diagnosis or treatment of Alzheimer’s, and thus amyloid PET scans are not covered as routine care.

Now, a study has been initiated to more definitively determine the clinical value of amyloid PET scanning. Over the next four years, the Imaging Dementia—Evidence for Amyloid Scanning (IDEAS) Study aims to enroll over 18,000 patients with possible but uncertain Alzheimer’s (following a standard diagnostic cognitive exam) and provide each with an amyloid scan to see whether that additional information can confirm or rule out an Alzheimer’s diagnosis. The study is sponsored by the Alzheimer’s Association.

As James Hendrix, Ph.D., the director of global science initiatives for the Alzheimer’s Association, told Psychiatric News, IDEAS has two broad aims. “First we want to see if these scans significantly affect patient management. Referring physicians will write up a full case report before the PET scans occur, basically stating, “How would I treat this patient today?,’ ” he said. “After they get the PET results, they can reassess based on the additional data, and we will look at the trends.”

The second aim will assess whether these scans—and any changes to the physician’s recommendations as a result—can change clinical outcomes such as hospitalization or emergency room visits over a 12-month period.

“The Alzheimer’s field is in an awkward phase right now where our ability to diagnose this disease far outpaces our ability to treat it,” said Gil Rabinovici, M.D., an associate professor of neurology at the University of California, San Francisco, and chair of the IDEAS study team. “So many of our strategies are reactive to changes in patient behavior, and we hope that incorporating PET scans can help shift us to a more proactive approach toward patient management and safety.”

Rabinovici noted that getting an accurate Alzheimer’s assessment at an early disease stage can help patients with financial or care plans, as well as improve their psychological well-being. However, it may also be a key component to help improve therapies, such as identifying patients who would be good candidates for amyloid antibody therapy. (Some research has suggested the lack of efficacy of amyloid antibodies may be due in part to having misdiagnosed patients with other types of dementia in the clinical trials.)

“We are not suggesting that PET scans are for everybody,” Hendrix said. “But we hope that they can provide a critical piece of information for physicians who have that case of diagnostic uncertainty and need additional help.”

In addition to the Alzheimer’s Association, the American College of Radiology and Society of Nuclear Medicine and Molecular Imaging, American Geriatrics Society, and other groups have been involved in the development, management, and promotion of this large undertaking, which will span 200 clinical sites across the United States. ■