Diagnostic Imaging
January 2003

OVERREAD

PET evaluation reduces Alzheimer's treatment costs

Quality of life improves with reduced drug therapy and delayed nursing home care

Some of the foremost authorities on molecular imaging and Alzheimer's disease have scored another point in the ongoing debate over the use of PET in diagnosing Alzheimer's disease. Using PET to diagnose Alzheimer's disease can lead to earlier treatment and lower costs of care, according to researchers at the University of California, Los Angeles.

"Appropriate use of PET in the evaluation of dementia can substantially improve patients' lives by cutting unnecessary drug therapy in half and avoidable nursing home care by 60%," said Dr. Daniel Silverman, head of neuronuclear imaging research at UCLA and lead author of a study published in the October 2002 issue of Molecular Imaging and Biology.

While several studies have reported that PET is useful in providing early diagnosis of Alzheimer's disease, it is regarded as too expensive to serve as a diagnostic exam for a disease that lacks a truly effective cure or treatment.

"You get extremely high sensitivity and specificity with PET when compared to just a clinical exam without the benefit of PET," said Dr. Gary Small, director of the UCLA Memory Clinic. "We've seen firsthand here the costs and complications involved with unclear diagnoses and deciding whether or not to treat these patients."

The UCLA researchers attempted to define how the use of PET would affect clinical outcomes, speculating that the change in treatment plan alone could substantially reduce the cost of care.

"This is the first systematic assessment of the positive difference brought about by the appropriate use of PET and the benefits its use will have on the lives of patients being evaluated for dementia," Silverman said.

Silverman and colleagues compared two strategies for determining whether Alzheimer's disease was the cause of cognitive decline in geriatric patients and for managing those patients. One followed the American Academy of Neurology's recommended standards for diagnosis. The second strategy also followed AAN recommendations but added PET imaging.

By including PET in the clinical workup of geriatric patients with cognitive decline, the researchers were able to decrease the rates of false negatives from 8.3% to 3.1% and false positives from 23% to 11.9%.

Silverman and colleagues combined this increased diagnostic accuracy with AAN recommendations for treating patients who do not have Alzheimer's disease. The number of avoidable months of nursing home care dropped by 62%, and unnecessary months of drug therapy dropped 48%.

"Patients who are diagnosed early with Alzheimer's disease can get the appropriate medication, and nursing home care can be put off for a time," Silverman said.

Data from empirical tests are coming in now, he said. Definitive results from prospective, randomized studies are five years away.

There is currently no treatment for Alzheimer's disease, which complicates the decision to add an expensive test like FDG-PET to the patient workup. A prospective study published in the November 6, 2002, issue of the Journal of the American Medical Association found that prior use of hormone replacement therapy reduced the incidence of Alzheimer's disease in women. Of 1066 women who were using HRT, 26 went on to develop Alzheimer's disease, compared with 58 of 800 women who were not on an HRT regimen. On the other hand, a study in the November 15 issue of Science found that promising vaccine treatments that had reached human trials seem to cause brain hemorrhaging in mice.

"We want to get more data on specific PET patterns and how they predict treatment responses," Small said. "Work is being done here at UCLA looking into new small molecule probes. These probes can get signals for concentrations of plaques and tangles in the brain, which may lead to faster drug development."