LONDON—Amyloid PET imaging may change the care plan for a large proportion of patients with mild cognitive impairment (MCI) or dementia, according to interim results presented at the 2017 Alzheimer’s Association International Conference. The most common change following PET imaging may involve pharmaceutical treatment. The study could influence the reimbursement of PET imaging for appropriately selected patients.
Amyloid PET imaging detects amyloid plaques in the brains of living people. The technique can clarify the diagnosis of patients with cognitive impairment of uncertain cause. In a 2013 National Coverage Decision, the Centers for Medicare and Medicaid Services stated that they would not reimburse clinicians for amyloid PET imaging because “the evidence is insufficient to conclude that the use of PET amyloid-beta imaging is reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of … Medicare beneficiaries with dementia or neurodegenerative disease.”
Examining Care Plans Before and After Imaging
Gil D. Rabinovici, MD, Professor of Neurology at the University of California, San Francisco, and colleagues initiated the Imaging Dementia Evidence for Amyloid Scanning (IDEAS) study with the goals of assessing the effect of amyloid PET on the patient care plan at three months, and assessing the scan’s effect on health outcomes at one year. More than 1,100 participating clinicians across the United States plan to enroll 18,500 Medicare beneficiaries with MCI or dementia of uncertain etiology.
Gil D. Rabinovici, MD
In the study, referring clinicians document their care plans for their patients before the patients undergo amyloid imaging. After patients undergo imaging, the clinicians receive the results and make recommendations accordingly. Patients return for a follow-up visit 90 days later. Finally, the clinicians record what management changes have been implemented.
Dr. Rabinovici reported the results of a prespecified interim analysis of the first 3,979 patients enrolled in the study. The analysis was intended to determine the feasibility of detecting a 30% change in the patient management plan. The composite end point includes changes in the use of medications specifically indicated for Alzheimer’s disease, changes in other neurologic medications, and finally, counseling about safety and future planning.
Most Patients’ Care Plans Changed
Approximately 64% of participants had MCI, and about 36% had dementia. The population’s mean age was 75. Approximately 51% of patients were women. In 76% of participants, the suspected cause of cognitive impairment was Alzheimer’s disease. PET scans were positive for 54.3% of patients with MCI and 70.5% of patients with dementia.
The care plan changed for 67.6% of participants, and the percentage change was similar between patients with MCI (67.8%) and those with dementia (65.9%). The most common change was in the use of Alzheimer’s-disease-specific medications (about 48% in the MCI and dementia groups), followed by the use of other neurologic medications (36.0% for the MCI group and 32.2% for the dementia group) and counseling (23.9% in the MCI group and 15.9% in the dementia group). “Each patient might have had changes in two, or even all three, of these components, and this would be counted as only one change in the composite for that patient,” said Dr. Rabinovici.
PET led to a more precise diagnosis and treatment plan for participants, he added. Among patients with a positive amyloid PET scan, the rate of Alzheimer’s disease diagnosis increased from 78.5% to 95.2%. In patients with a negative scan, the rate of Alzheimer’s diagnosis decreased from 73.0% to 14.5%. “Many patients would have otherwise been diagnosed with Alzheimer’s disease, and yet there was no biologic evidence of amyloid plaques in the brain,” said Dr. Rabinovici.
These changes in diagnosis led to appropriate treatment. For patients with a positive scan, the use of Alzheimer’s-disease-specific drugs increased from 50.9% to 83.8%. For patients with a negative scan, the use of these drugs decreased from 39.1% to 30.8%.
“The pivotal trials for cholinesterase inhibitors and memantine in Alzheimer’s disease did not require a biomarker, so we do not really know that only amyloid-positive patients benefit,” said Dr. Rabinovici. “Also, patients with Lewy body dementia have been shown to benefit from cholinesterase inhibitors, and [they] can be negative on amyloid PET.”
Imaging May Dispel Uncertainty
“These are partial results reflecting one-third of the sample,” said Dr. Rabinovici. Recruitment is ongoing and may be complete by early 2018. After enrollment is complete, a year of follow-up will be required to determine whether amyloid PET improves participants’ outcomes. The researchers may finish the study earlier than they had anticipated, and final results pertaining to changes in management may be available in one year.
“One thing that this study is not capturing is the meaning of diagnosis,” said Dr. Rabinovici. “Patients want to know what is going on in their brain. They want to understand what the cause of cognitive impairment is…. A lot of times, the uncertainty is worse than the certainty, even when the information is bad news.”
—Erik Greb
Suggested Reading
Jack CR Jr, Barrio JR, Kepe V. Cerebral amyloid PET imaging in Alzheimer’s disease. Acta Neuropathol. 2013; 126(5):643-657.
Johnson KA, Minoshima S, Bohnen NI, et al. Appropriate use criteria for amyloid PET: a report of the Amyloid Imaging Task Force, the Society of Nuclear Medicine and Molecular Imaging, and the Alzheimer’s Association. Alzheimers Dement. 2013;9(1):e-1-16.
Vandenberghe R, Adamczuk K, Van Laere K. The interest of amyloid PET imaging in the diagnosis of Alzheimer’s disease. Curr Opin Neurol. 2013;26(6):646-655.