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Thursday, November 05, 2015

Hope for Using Amyloid Pet Imaging in Clinical Care


Dear Readers,

Preclinical biomarkers that may predict progression from normal cognition to MCI and Alzheimer’s disease (AD) were included in the latest criteria and guidelines for the diagnosis of Alzheimer’s disease from the National Institute on Aging (NIA) and the Alzheimer’s Association (Sperling et al., 2011). One such biomarker is positron emission tomography (PET) amyloid imaging. When conducted according to established protocols, a positive PET scan is taken as consistent with moderate to frequent amyloid as visualized on a post-mortem exam, while a negative scan is consistent with sparse to no amyloid. Both positive and negative scans can be useful in the diagnosis of the cause of dementia (Zannas et al., 2014).

As with other biomarkers, amyloid PET imaging can be positive in the earliest disease stages, before clinical symptoms appear. As there is a developing consensus that early diagnosis and treatment may be essential for effective intervention, amyloid PET imaging is poised to have a significant impact in the clinic and in the selection of patients for clinical trials aimed at developing disease-specific therapies (Sperling et al., 2011).

In the fall of 2013, the Centers for Medicare & Medicaid Services (CMS) issued a decision memorandum stating that the evidence was insufficient to conclude that amyloid PET imaging was reasonable and necessary for the clinical diagnosis or treatment of AD. They ruled that Medicare would not cover the procedure as a routine clinical test. Other third-party payers followed Medicare’s lead. Thus, although the procedure has been approved by the FDA for clinical use and is widely available, in clinical practice it can be utilized only by those able to afford the approximately $3,000 out-of-pocket expense. CMS did make an exception for specific cases involving difficult differential diagnoses, such as AD versus frontotemporal dementia. In addition, CMS ruled that it would cover one amyloid PET scan per patient for CMS-approved clinical studies meeting specific criteria.

The CMS memorandum posed several questions meriting further study, including whether amyloid PET imaging leads to meaningfully improved health outcomes, including avoidance of futile treatment or tests, improving (or slowing the decline of) quality of life, and survival. Another question was whether specific variables could be identified - subpopulations, patient characteristics, or differential diagnoses – that predict enhanced health outcomes when management was guided by amyloid PET imaging. These questions have been addressed by several clinical investigations (Camus et al., 2012; Clark et al., 2012; Doraiswamy et al., 2014; Grundman et al., 2013) and case reports (Mitsis et al., 2014; Zannas et al., 2014). The following case series exemplifies the use of clinical amyloid PET imaging by specialists in dementia care. In each case, scan results were used to refine a diagnosis, change a treatment, avoid unnecessary tests and medications, encourage participation in clinical trials of anti-amyloid therapies, and/or facilitate personal planning, both legal and occupational.

Because there is an interest in utilizing the amyloid PET imaging as part of the diagnostic evaluation of Alzheimer’s dementia, CMS has agreed to support a demonstration grant called the IDEAs. In this study, over 18,000 amyloid PET scans will be acquired in people with Mild Cognitive Impairment or in dementias that are difficult to distinguish in order to determine if, after 3 and 12 months, clinical decision-making will be influenced by the acquisition of the PET scan. It is hoped by many researchers, including myself, that amyloid PET will be reimbursed so it can be used. In selected patients, it can be useful in excluding AD dementia or increasing the probability thus influencing clinical decision making and directing treatment.

Marwan Noel Sabbagh MD, FAAN
Professor of Neurology
Director, Alzheimer’s and Memory Disorders Division
Barrow Neurological Institute
Research Professor of Neurology, UA College of Medicine-Phoenix

 
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The Alzheimer's Disease Cooperative Study (ADCS) was formed in 1991 as a cooperative agreement between the National Institute on Aging (NIA) and the University of California, San Diego. The ADCS is a major initiative for Alzheimer's disease (AD) clinical studies in the Federal government, addressing treatments for both cognitive and behavioral symptoms. This is part of the NIA Division of Neuroscience's effort to facilitate the discovery, development and testing of new drugs for the treatment of AD and also is part of the Alzheimer's Disease Prevention Initiative.

The ADCS was developed in response to a perceived need to advance research in the development of drugs that might be useful for treating patients with Alzheimer's disease (AD), particularly drugs that might not be developed by industry.