DMS Blog

The Current Status of Alzheimer’s PET Imaging

Alzheimer’s disease is the sixth leading cause of death in the United States. Around one in three American seniors die from Alzheimer’s or another dementia, making it a bigger killer than breast and prostate cancer combined.

In fact, deaths from Alzheimer’s disease increased 145% between 2000 and 2017 and it is estimated that 10% of people over 65 have the disease.

While the underlying disease cannot be stopped at this time, early diagnosis is very beneficial to patients and their families. Receiving treatment early can help to preserve daily functioning for a longer period and allows the patient and their family time to plan for the future. It’s preferable that things like legal and living arrangements are made while the patient is able to make decisions for themselves.

This is where it gets complicated – Alzheimer’s disease is notoriously difficult to diagnose. One reason for this is that patients often under-report their symptoms. Doctors might make a diagnosis of “probable” or “possible Alzheimer’s dementia,” but they can usually only go by what patients and their families are reporting, along with testing to rule out other possible causes of symptoms.

It used to be that the only definitive way to diagnose Alzheimer’s was during autopsy, when the brain could be physically examined for the deterioration that is indicative of Alzheimer’s. Amyloid PET imaging allows physicians to verify the presence of amyloid plaques, which increase the clinical certainty of an Alzheimer’s Disease diagnosis.

The amyloid plaques are a hallmark of Alzheimer’s disease and detecting them can help to provide an early diagnosis and subsequent action plan for the living patient.

What is an Amyloid PET scan?

The purpose of an Amyloid PET scan is to detect on imaging (or to rule out the presence of) amyloid plaques on the brain. A chemical tracer is injected into the patient prior to a Positron Emission Tomography (PET) scan. The tracer travels to the brain and if amyloid proteins are present, it will stick to them and make them show up on images.

Amyloid plaques may be present in someone with an otherwise normally-functioning brain and can be an indicator of other cognitive impairment conditions apart from Alzheimer’s disease. Researchers have also found that amyloid plaques may be present one or two decades prior to Alzheimer’s symptoms appearing, so it can be a very early sign.

It’s also important to note that not everyone who has signs of amyloid plaques has or will develop Alzheimer’s disease. However, detecting these plaques, along with other cognitive symptoms can help to provide a clear diagnosis, where previously patients were “probable.”

For this reason, indications for an Amyloid PET scan should include patients who have unexplained mild cognitive impairment, meet core clinical requirements for Alzheimer’s or who have progressive dementia and symptoms of early onset.

PET detection of amyloid plaque can aid in the diagnosis of Alzheimer’s disease

What’s next after the Amyloid PET scan?

In the treatment of Alzheimer’s disease, the positive indicator for amyloid plaque on the brain is just the beginning for the patient. What happens next?

If amyloid plaque is detected, then physicians can make a more informed diagnosis of Alzheimer’s disease. With this in-hand, the patient, their physician and their family can devise a plan to prolong their functioning abilities and to prepare for such a time as when they’re no longer able to manage daily life without help.

Another possible outcome is access to drug trials for Alzheimer’s disease. There are many such trials which require a positive Amyloid PET scan in order to gain access. Given the difficulty with definitively diagnosing Alzheimer’s, scientists want to be sure that the people participating in their trials truly do have the disease.

This has been an issue that PET scans have helped with. It has been found that many people being treated for Alzheimer’s disease don’t in fact have it. While the presence of amyloid plaque doesn’t always indicate Alzheimer’s disease, no presence of amyloid plaque means the patient does not have the disease.

A PET scan resulting in no Alzheimer’s diagnosis can significantly change the care plan of the patient. Physicians can then look for other underlying causes of the patient’s symptoms. For example, sometimes they may be related to sleep disturbances, vitamin deficiencies, mood disorders, mercury toxicity or other causes of cognitive impairment.

This is very important for patients as further medical examination where no plaque is present can find a cause for their decline that is treatable. In some cases where the patient did not have Alzheimer’s they have gone back to living a normal life with no decline when the true root cause was discovered and treated.

Another important factor for the patient is that if they do not have Alzheimer’s disease, then treatment with (often expensive) medications can be stopped and alleviate any undue financial burden to the patient, family or their caregivers. These medications often have uncomfortable side-effects for patients too, so it is preferable to stop them.

The IDEAS study

The recently-published IDEAS (Imaging Dementia – Evidence for Amyloid Scanning) study examined data on how Amyloid PET imaging changed physicians’ diagnosis and choice of treatment for their patients.

Results were significant. In more than 60% of cases, doctors changed their prescribed course of medical management for the patient due to the imaging results. This was more than double what researchers had hypothesized at the start of the trial.

They also found that doctors were more than twice as likely to prescribe Alzheimer’s medication if images showed amyloid plaque. There were also many cases where Alzheimer’s medication was discontinued following a scan with no evidence of amyloid plaque.

This was just the first phase of the study – the second phase is due to publish in 2020.

Alzheimer’s PET Imaging

Final thoughts

Amyloid PET imaging is proving to be a useful breakthrough for Alzheimer’s disease patients and for other patients experiencing cognitive symptoms.

Where once Alzheimer’s could only be definitively diagnosed during autopsy, now, thanks to PET imaging, the amyloid plaques that are a hallmark for Alzheimer’s can be detected on the brains of patients. This is a key step for managing Alzheimer’s disease as early as possible, potentially giving patients more quality time and allowing them and their families time to prepare.

Conversely, PET imaging can definitively show when a patient does not have Alzheimer’s disease. This can prompt physicians to run more rigorous investigations to find the root cause of the patient’s symptoms. In some cases, this results in the discovery of something that is treatable, allowing the patient to return to normal life.

Overall, Amyloid PET represents more peace of mind for patients and physicians in terms of getting a more reliable diagnosis. It can prove to be a game-changer for treatment plans.

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