Mark Schechter, MD, Medical Director of Nuclear Medicine and PET Imaging, Imaging Healthcare Specialists
It’s darkly ironic that we know so little about Alzheimer’s disease (AD), a disease that slowly grinds the brain to a halt. It’s a disease for which there is no known cure—the only disease among the 10 most common causes of death in the United States to hold such a distinction. More than 5 million people in the United States have AD (one out of every eight persons over the age 65), and, with an aging population, that number is likely to increase, as is the estimated $400 billion of direct and indirect cost of care AD causes. While the search for a viable treatment continues, the diagnostic side of AD care has a new tool that allows doctors to probe more deeply into a patient’s condition. The new weapon in the fight against AD is PET brain imaging with Amyvid™. Amyvid, a radioactive agent that highlights beta-amyloid neuritic plaques, the pathologic hallmark of AD, was recently approved by the FDA and is the only PET tracer of its kind currently available.
“We’re seeing thousands of patients [with dementia] every year,” said Mark Schechter, MD, medical director of nuclear medicine and PET imaging for Imaging Healthcare Specialists. “The most common imaging exams that we are asked to perform are CT and MRI of the brain—routine structural imaging. The clinical accuracy of diagnosing AD is roughly 80%. For many patients, the diagnosis is obvious to the clinician, but it’s in patients who are already demented. Now, a probable imaging diagnosis of AD is possible in patients who are only mildly impaired and not yet demented.”
The five main biomarkers of AD occur at different points on the timeline of the disease, which can stretch for more than a decade. “Prior to a patient becoming demented, they develop mild cognitive impairment (MCI),” Schechter said. “That’s the first symptom of dementia.” Symptoms of MCI include memory loss, but the patient is still able to function independently. “Once a patient is demented, that means they have irreversible dysfunction that has resulted in cell death, atrophy, and destruction of the brain tissue,” he said. “There’s nothing you can do about it at that point. Our efforts clinically are directed at the MCI group. It’s in that group of patients that this test could have an incredible impact.”
The appearance of amyloid plaques in the brain is among the first biomarkers to appear, and one that occurs in patients who are cognitively normal, 10 to 15 years before symptoms show up. “If you take 100 patients who have AD, and if you could image their brain 10 years before they were symptomatic, roughly 90% of the patients would be positive on imaging tests like Amyvid,” Schechter said. In comparison, tests like MRI are positive only after the patient is deep into AD territory, on the far right of the timeline.
Schechter says that not everyone finds PET imaging with Amyvid useful. To some patients, doctors, and insurers, diagnosing that which cannot be cured is an unnecessary expense that adds little to a patient’s outlook. Schechter disagrees with that assessment on several levels. First, he says confirming a diagnosis can bring peace of mind to a patient’s family and allow them to plan for the future appropriately. Second, a negative Amyvid scan means AD is unlikely to be the cause of a patient’s impairment and physicians should consider other diagnoses. On a larger plane, Schechter says that having the diagnostic side of AD care in place for whenever researchers find a feasible treatment or cure will be essential to its effectiveness. “Once we do get a drug that can reverse or stop AD, it would be mandatory they would take a test like this,” he said. In addition to confirming an AD diagnosis, a PET brain imaging scan with Amyvid could be used to track the effectiveness of an eventual treatment.
Although the technology has been in research for a while, its availability to the larger population holds promise, according to Schechter. “Until recently, these tools have not been available to community physicians,” he said. “It’s very exciting to be at the forefront of that.”
