PHILADELPHIA – The radioimaging agent 18F-florbetaben reliably excluded amyloid pathology in a study of 74 end-of-life patients with dementia.
When used in PET brain scans, the agent showed 98% sensitivity for beta amyloid plaques, with a 96% negative predictive value, Dr. Marwan N. Sabbagh said at the annual meeting of the American Academy of Neurology.
"A negative scan should encourage the physician to search for other causes of cognitive decline and to tailor available treatment options," said Dr. Sabbagh, director of the Banner Sun Health Research Institute in Sun City, Ariz.
The study comprised 205 elderly patients who were near the end of life and had agreed to post mortem brain histopathology. The PET scans were read by three radiologists who had been trained in person on the use of the agent. Histopathology confirmed the scan results.
Dr. Marwan N. Sabbagh
Of the group, 74 patients had both scans and histopathology verification. Most (57) had a clinical diagnosis of Alzheimer’s disease; three had been diagnosed with Lewy body dementia; and six were diagnosed with "other" dementia. Eight subjects were not demented at the time of death.
On histopathology, 47 of the patients showed amyloid pathology: 44 of the Alzheimer’s patients; 1 of the Lewy body patients; 1 of the "other dementia" patients; and 1 of the nondemented patients.
Florbetaben scans correctly identified amyloid plaques in 44 of these 47 patients, for a sensitivity of 98%. Scans from 24 of the 27 patients without amyloid pathology were correctly read as negative, for specificity of 89%. All but one of the 25 scans read as negative were confirmed negative by histopathology, for a negative predictive value of 96%.
These values are slightly better than those seen with 18F florbetapir (Amyvid), the PET imaging agent approved in 2012. It has a sensitivity of 92% and specificity of 95% for readers who received individual training in reading the scans. Both agents have a half-life of about 2 hours.
Florbetaben (NeuroCeq) received Food and Drug Administration approval in March, making it the third amyloid imaging compound approved for use in the United States.
A fourth, NAV4694, is being developed by Navidea Biopharmaceuticals. In early studies, the company said that the agent has a sensitivity, specificity, and overall accuracy ranging from 94% to 98%.
Avid Radiopharmaceuticals, the maker of 18F-florbetapir, is owned by Eli Lilly.
Piramal Imaging, maker of 18F-florbetaben, funded the study. Dr. Sabbagh has received grant money from the company as served as an adviser. He also disclosed that he has received grant money from Avid Radiopharmaceuticals.
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