Society of Nuclear Medicine and Molecular Imaging 2021 Annual Meeting – Key takeaways.
The Society of Nuclear Medicine and Molecular Imaging held their annul meeting earlier this month which provided some interesting insights on new radiotracer studies and clinical trials. We take a look at the new methods and what the results mean.
New PET tracer detects hallmark of Alzheimer's disease years before symptoms emerge
A novel positron emission tomography (PET) radiotracer has been shown to effectively measure increases in brain tau—a distinguishing characteristic of Alzheimer’s disease—before any symptoms of the disease are observed. With the potential to measure increases in tau over a long period of time, this tracer offers an important tool to assess the effectiveness of Alzheimer’s disease treatments in clinical trials.
Tau is a protein commonly found in healthy brain neurons. In people with certain brain disorders, like Alzheimer's disease, chemical changes cause tau proteins to accumulate in various parts of the brain. As such, tau is valuable as a biomarker for measuring disease progression.
In the study, researchers sought to detect patterns and rates of tau accumulation in both a cognitively normal aging population and in those with Alzheimer's disease. PET imaging with the novel radiotracer 18F-MK6240 was performed on all participants at baseline and after 12 months. After each scan, uptake of the radiotracer was measured in multiple areas of the brain.
Increases in tau were measured in both participant groups and longitudinal tau imaging was effective in discriminating between the two cohorts. The uptake of 18F-MK6240 was higher at baseline and after one year in participants who were on the Alzheimer's disease continuum in comparison to the cognitively normal aging participants.
Christopher Rowe, BMBS, FRACP, MD, FAANMS, Director of Molecular Imaging Research at Austin Health and Director of the Australian Dementia Network in Melbourne, Australia commented, "the effectiveness of the 18F-MK6240 tracer is important for drug trials that aim to measure whether or not treatments to remove tau from the brain are actually working. Use of the radiotracer will allow researchers to select people at different stages of Alzheimer's disease for clinical trials, which ultimately may speed the development of effective treatments for the disease."
This, paired with the FDA’s recent approval of a new drug to treat Alzheimer’s, is a credible step to discover how Alzheimer’s develops in patients and hopefully the right step in finding new treatments.
PSMA-Targeted Radiotracer Pinpoints Metastatic Prostate Cancer Across Anatomic Regions
A phase III clinical trial has validated the effectiveness of the prostate-specific membrane antigen (PSMA)-targeted radiotracer 18F-DCFPyL in detecting and localizing recurrent prostate cancer. Approved by the U.S. Food and Drug Administration last month, the radiotracer identified metastatic lesions with high positive predictive values regardless of anatomic region, adding to the evidence that PSMA-targeted radiotracers are the most sensitive and accurate agents for imaging prostate cancer.
Prostate cancer patients have high levels of PSMA expression, which makes PSMA an effective target for imaging the disease. In previous studies, the novel positron emission tomography (PET) imaging agent 18F-DCFPyL was found to bind selectively with high affinity to PSMA. To demonstrate the diagnostic performance of 18F-DCFPyL for regulatory approval, a prospective, multicentre study was conducted in 14 sites across the United States and Canada.
The study sought to determine the positive predictive value (the probability that patients with a positive screening test actually have the disease) and detection rate of 18F-DCFPyL PET/computed tomography (CT) by anatomic region, specifically the prostate/prostate bed, pelvic lymph nodes, and regions outside the pelvis. Study participants included men who had rising prostate-specific antigen (PSA) levels after local therapy as well as negative or equivocal conventional imaging results.
Patients were imaged with 18F-DCFPyL PET/CT, then imaged again after 60 days to verify suspected lesions using a composite “standard of truth,” which consisted of histopathology, correlative imaging findings and PSA response. Comparing findings between the 18F-DCFPyL imaging and the “standard of truth,” the positive predictive value and detection rate were measured.
18F-DCFPyL-PET/CT was found to successfully detect and pinpoint metastatic lesions with high positive predictive value, regardless of their location in the body, in men with biochemically recurrent prostate cancer who had negative or equivocal baseline imaging. Higher positive predictive values were observed in extra-pelvic lymph nodes and bone compared to soft tissue regions.
With the recent approval of 18F-DCFPyL (now referred to as piflufolastat F-18) by the FDA, the impact of this research may be realized in the very near future. As these agents become more widely available, patients with newly diagnosed, recurrent, and metastatic prostate cancer may have new therapeutic approaches available to them. The results of the study will be presented at the SNMMI meeting by Steven Rowe, MD, PhD, associate professor of radiology and radiological science at Johns Hopkins University in Baltimore, Maryland.
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