Dr Clifford Jack, Jr., MDClifford Jack, Jr., MD
According to the results of the US-wide, practice-based Imaging Dementia-Evidence for Amyloid Scanning (IDEAS) study, in patients with mild cognitive impairment or dementia of uncertain etiology, amyloid positron emission tomography (PET) imaging was associated with changes in clinical management within 90 days.

After analysis of 11,409 patients, researchers found that patient management 90 days after amyloid PET changed in 60.2% of patients with mild cognitive impairment and 63.5% of patients with dementia.

“An important finding was the discrepancy between presumed etiology underlying impairment based on standard of care clinical assessments pre-PET, and the etiology as informed by amyloid PET,” Clifford Jack Jr., MD, a professor of radiology at the Mayo Clinic, and Ronald Petersen, MD, PhD, professor of neurology at the Mayo Clinic, wrote in an accompanying editorial.1 “These data highlight the disconnect between presumed etiology of impairment based on syndromic presentation alone and the underlying biology based on biomarker or neuropathologic evidence and has important implications for future clinical trials.”

The objective of IDEAS, launched in 2016, was to assess the association between amyloid PET and succeeding changes in clinical management and health outcomes in those with mild cognitive impairment or dementia of uncertain cause.

There were a total of 946 recruited dementia specialists at 595 U.S. sites that enrolled 16,008 Medicare beneficiaries between February 2016 and September 2017. Patient follow-up continued through January 2018. Under the Coverage with Evidence Development policy, the Centers for Medicare and Medicaid Services (CMS) reimbursed amyloid PET scans conducted at 343 facilities and interpreted by more than 733 imaging specialists. Specialists documented diagnoses and management plans prior to PET and again 90 days after PET.

The primary outcome measure was the change in management between the pre- and post-PET visits, assessed by a composite outcome that included Alzheimer disease drug therapy, additional drug therapy, and safety counseling and future planning. The secondary endpoint included the change in diagnosis from Alzheimer disease to non-Alzheimer disease and vice versa between pre- and post-PET visits.

Of the 11,409 (71.3%) that completed study procedures and were included in the analysis, 6905 (60.5%) were diagnosed with mild cognitive impairment and 4505 (39.5%) were diagnosed with dementia. Amyloid PET results were positive in 3817 (55.3%) patients with mild cognitive impairment and in 3153 (70.1%) with dementia.

Researchers reported that changes between the pre-PET and post-PET management occurred in 60.2% (95% CI, 59.1%–61.4%) of patients with mild cognitive impairment and 63.5% (95% CI, 62.1%–64.9%) of patients with dementia, which exceeded the target of 30% composite change in each group. Physicians reported that PET results contributed greatly to the post-PET management plan in 85.2% of cases where a change was made. The etiologic diagnosis changed from Alzheimer disease to non-Alzheimer disease in 2860 of 11,490 patients (25.1%) and from non-Alzheimer disease to Alzheimer disease in 1201 of 11,490 patients (10.5%).2

The most frequent change in management involved Alzheimer disease drug use, which changed in 43.6% (95% CI, 42.5%–44.8%) of patients with mild cognitive impairment and 44.9% (95% CI, 43.4%–46.3%) of patients with dementia. Researchers reported that changes in non-Alzheimer disease drug occurred in 22.9% (95% Ci, 21.9%–23.9%) of patients with mild cognitive impairment and 25.4% (95% CI, 24.1%–26.7%) of patients with dementia. Changes in counseling were reported in 24.3% (95% CI, 23.3%–25.4%) of patients with mild cognitive impairment, and 20.7% (95% CI, 19.6%–21.9%) of patients with dementia. Changes were reported more common in those with positive PET results vs. negative.

The rate of Alzheimer disease diagnosis increased from 80.3% (95% CI, 79.3%–81.2%) pre-PET to 95.5% (95% CI, 94.9%–95.9%) post-PET in those with a positive scan result, while those with negative scan results saw a decreased rate of diagnosis from 71.5% (95% CI, 70.2%–72.8%) pre-PET to 10.2% (95% CI, 9.3%–11.1%) post-PET.

Among Medicare beneficiaries with mild cognitive impairment or dementia of uncertain cause, the use of amyloid PET was associated with changes in clinical management within 90 days; further research is needed to determine if amyloid PET is associated with improved clinical outcome.

“Although the findings of the IDEAS study show that improved knowledge about etiology provided by amyloid PET, over and above current standards of clinical care, changes clinical management, there are important nuances to this broad conclusion,” Jack and Petersen concluded.

Researchers are currently analyzing data from the second aim of the study, which examined how amyloid PET scans at 12 months affect health outcomes following the scan. Medicare claims data were used to compare health outcomes and overall resource utilization in for patients enrolled in the study with a matched control cohort of Medicare beneficiaries who have not undergone amyloid PET. The primary objective is to determine if amyloid PET testing in the amyloid PET-known cohort is associated with a significant reduction in major outcomes.3
REFERENCE
1. Jack Jr. C, Petersen R. Amyloid PET and Changes in Clinical Management for Patients With Cognitive Impairment. JAMA. 2019;321(13):1258­–1260.
doi: 10.1001/jama.2019.1998.
2. Rabinovici G, Gatsonis C, Apgar C, et al. Association of Amyloid Positron Emission Tomography With Subsequent Change in Clinical Management Among Medicare Beneficiaries With Mild Cognitive Impairment or Dementia. JAMA. 2019;321(13):1286–1294. doi: 10.1001/jama.2019.2000.
3. About IDEAS. IDEAS, Imaging Dementia–Evidence for Amyloid Scanning website. ideas-study.org/about/. Accessed April 3, 2019.