PET Scans Improve Management of Patients with Dementia

A national study has found that positron emission tomography (PET), a form of brain imaging that detects Alzheimer's-related "plaques," significantly influenced clinical management of patients with mild cognitive impairment (MCI) and dementia. The results of the study were recently published in JAMA.

The research team, which is part of the IDEAS study, enrolled a total of 16,000 Medicare beneficiaries. For this initial phase, the primary endpoint was how physicians altered participant's medication prescriptions and counseling about safety and future planning. The researchers found that in MCI patients with significant amyloid deposits, physicians were twice as likely to prescribe Alzheimer's drugs after positive PET imaging. In those with dementia, prescriptions rose from 63% pre-PET to 91% following positive amyloid imaging. A number of patients with MCI and dementia and negative amyloid imaging were taken off Alzheimer's medications. This indicates an improvement in appropriate drug prescribing for Alzheimer's patients.

For the secondary endpoint the scientists determined if PET imaging results caused physicians to change the patient's diagnosis. The authors found that diagnoses changed from Alzheimer's disease to non-Alzheimer's in 25% of patients, and from non-Alzheimer's to Alzheimer's in 11% of participants. And based on imaging results, physicians were able to ensure that 93% of patients referred to Alzheimer's trials were amyloid-positive.

The researchers found that changes in counseling were reported in 24% of patients with MCI and 21% of patients with dementia. Specialists were more likely to make changes in care compared to nonspecialists. Changes in all aspects of care management of patients were more common in patients with positive versus negative amyloid PET scan results.

Gil Rabinovici, MD, distinguished professor of Neurology at the University of California at San Francisco Memory and Aging Center was the study lead author and principal investigator He said "We are impressed by the magnitude of these results, which make it clear that amyloid PET imaging can have a major impact on how we diagnose and care for patients with Alzheimer's disease and other forms of cognitive decline." Maria C. Carrillo, PhD, Alzheimer's Association chief science officer and a co-author of the study, said, "These results present highly credible, large-scale evidence that amyloid PET imaging can be a powerful tool to improve the accuracy of Alzheimer's diagnosis and lead to better medical management, especially in difficult-to-diagnose cases. It is important that amyloid PET imaging be more broadly accessible to those who need it."

I view this as a landmark study with real world evidence showing dramatic outcomes in terms of the impact of the PET scan on diagnosis, appropriate drug therapeutics, and some data on care counseling of patients. I am especially proud that the ADDF provided funding for the first PET scan that was approved by the FDA (Amyvid™) in 2012 as a diagnostic tool for Alzheimer's.

Currently, Medicare does not pay for the Amyvid™ PET scan, which can cost between $3,000 to $5,000. I testified at an FDA hearing that Medicare should pay for it as the cost is a barrier to patients, and as a result, it is underutilized. I was joined in this opinion by many colleagues in my field. And I was heartened that JAMA study co-author Dr. Carrillo stressed, "It is important that amyloid PET imaging be more broadly accessible to those who need it."

As the researchers noted, the test has both prognostic value and can help doctors talk to patients and their families about what steps they should take now. As a practicing geriatrician, I know that education and counseling are valuable and a source of comfort to both patients and families. And of course, if there is a negative result, meaning no plaques, it is a great sense of relief to the person tested. The article also points out this is the first of many biomarkers people will need for Alzheimer's and dementia. This is the reason the ADDF created the Diagnostics Accelerator. Critical to advancing clinical research, we need to develop innovative blood tests that will be less expensive and less invasive than PET or spinal fluid tests for classifying patients.

Using the biomarker specific model of precision medicine, we will be able to predict more accurately which treatment and prevention strategies will work in different at-risk populations of people who have Alzheimer's disease or other forms of dementia, as we can now do in cancer, heart diseases, and other chronic diseases of aging and old age. Ultimately, biomarkers can determine which therapies would be most effective for an individual. Researchers are currently involved in phase two of the IDEAS study, which is examining how amyloid PET scans affect health outcomes after a scan is completed. These findings are expected to be published in 2020. Despite the very positive results thus far, Medicare still does not pay for the test.