Amyloid Imaging: The Next Frontier in Alzheimer’s Care

With the FDA approval last month of the radioactive diagnostic agent florbetapir, the industry continued the trend toward improved identification of beta-amyloid, the brain plaque associated with Alzheimer’s disease. Questions still exist about how best to use these tracers, but industry experts view these developments as significant positives for patient care.

Having another tracer available to use when imaging patients with suspected Alzheimer’s will also benefit providers, said Satoshi Minoshima, MD, PhD, director of the Neuroimaging and Biotechnology Laboratory at the University of Washington in Seattle.

“From an imaging point of view, Alzheimer’s and radioactive tracers that target amyloid will be one of the major research efforts over the next several years,” he said. “Therapeutically, now we can see amyloid deposition in the brain, and that will help drug companies develop more effective treatments and drugs.”

As a radioactive tracer, florbetapir binds to beta-amyloid plaque to make it visible through PET scans of the brain. Under the brand name Amyvid, it is the only FDA-approved imaging agent for amyloid plaque on the market, but it’s by no means the only one on the industry’s radar screen. Last year, GE’s flutemetamol entered Phase III clinical trials, and Pittsburgh compound B (PiB) has been used in Alzheimer’s research since 2002.

It’s this growing list of radioactive tracers that has the Society of Nuclear Medicine (SNM) anticipating the industry will make a greater clinical impact with Alzheimer’s, as well as other conditions. Making molecular imaging agents more readily available could open doors for more clinical research and clinical trials.

“We are hopeful that this will set the stage for the approval of the many other molecular imaging agents for cancer, cardiovascular disease, and other neurological diseases that are currently in clinical trials,” SNM president George Segall, MD, said in a statement. “The more molecular imaging agents available, the more options we have for diagnosing illness and ultimately enhancing patient care.”

And, that’s what one vendor has tried to do. In April, Siemens rolled out a first-of-its-kind integrated PET diagnostic imaging system that can detect beta-amyloid in the living brain. The PET system, currently under FDA review, includes the new Biograph mCT™ PET•CT scanner, syngo.PET Amyloid Plaque neurology quantification software, and florbetapir.

According to Edgar Alvarez, neurology segment lead for molecular imaging at Siemens, after imaging the brain, the system automatically compares a patient’s scan with a reference PET scan. This evaluation gives radiologists an additional tool and added confidence when they conduct visual assessments and make diagnoses. It could also be the beginning, he said, of using diagnostic imaging as a way to tailor Alzheimer’s therapies.

“This is a new frontier and a new era of healthcare in terms of personalized medicine,” Alvarez said. “In terms of imaging, we’ve made the first true steps toward new propriety biomarkers, opening up a new era of being able to intelligently identify patients who will best be served by the protocols and procedures we have to treat Alzheimer’s. It’s the dawn of a new era.”

Even with the excitement over growth in this area and the emerging trend toward using more radioactive tracers with Alzheimer’s, there is still some reticence about how the new capability will be employed. The main sticking point has been that radiologists and radiologic technologists might not have enough training to accurately read these PET studies. To mitigate this worry, the FDA, when it approved florbetapir, mandated those who would read the images receive extensive education on how to provide consistent and reliable interpretations.

The SNM and Alzheimer’s Association have also responded to this concern by forming a committee to draft appropriate use criteria. The goal, according to Minoshima, who also serves as the committee’s chair, is to determine how these tracers and the accompanying technology can provide the greatest benefits to patients.

Ultimately, the committee’s decisions, and the tracers themselves, will impact how you practice, he said.

“We must be careful about remembering that these studies can’t be used alone. They basically are there to support other clinical findings,” Minoshima said. “For example, if an image comes back amyloid-positive, but the patient isn’t demented, then it isn’t of much use yet. But these advanced imaging technologies are important because they can inform and be used with standard clinical variations in the future.”

Positive amyloid scan:

Negative amyloid scan:

Images courtesy Siemens