The rise of GLP-1 receptor agonist drugs prescribed for weight loss and type 2 diabetes could be compromising the interpretation of some cancer scans and throwing doctors off course.
This is the discovery of UK-based researchers who found the medications—known to alter glucose metabolism, stomach function and the body’s stress and energy system—may lead to “unique uptake” patterns of FDG PET-CT scans.
This is a combined imaging technique used to help identify areas of high metabolic activity like tumors or inflammation.
In previous case reports, there has been increased FDG uptake in skeletal muscle, heart muscle and brown adipose tissue (fat that burns energy to produce heat), which could be mistaken for cancer or inflammatory disease.
In the new research by Alliance Medical Ltd—presented today at the 38th Annual Congress of the European Association of Nuclear Medicine—the team performed a retrospective case series review of these scans in patients taking GLP-1 agonists.
They observed a number of unusual patterns of “tracer uptake” (the safe radioactive chemical used to highlight disease) that could be misinterpreted as disease if a patient’s medication history is not considered.
“We noticed unusual uptake in one of our patients on a GLP-1 agonist, which prompted a wider review across our network,” explained lead author Dr. Peter Strouhal, medical director at Alliance, in a statement. “We found that these altered patterns are increasingly common, yet there is currently no national or international guidance in the UK addressing this emerging issue.”
There also doesn’t appear to be official national guidelines on this in the U.S. either, though other emerging research may indicate a similar link.
The authors note, however, that Australian guidance suggests continuing treatment, fasting from midnight, scheduling morning scans and ensuring good glucose control.
Misinterpreting the patterns in scans as detected in this study could lead to unnecessary investigations, inappropriate cancer staging (determining the size of a tumor and its activity) and delays in treatment, the researchers have warned. As well as medical implications, this could also lead to stress for patients.
“Recognizing the characteristic uptake associated with GLP-1 agonists helps avoid unnecessary anxiety and interventions, ensuring patients receive the right care, at the right time, without detours or doubt,” Dr. Strouhal added.
Currently, based on these findings, the researchers don’t recommend changing patient preparation or stopping GLP-1 agonists before FDG PET-CT scans. They urge imaging teams to carefully document patients’ medication histories to help with interpretation while formal guidance is developed.
The researchers plan to extend their investigation across more imaging centers to help provide evidence for any guidelines, as well as to collaborate internationally on this for the benefit of patients around the world.
Newsweek has reached out to the team for additional comment.
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Reference
Strouhal, P., Meadows, A., & McGovern, A. (2025). A weighty problem: GLP-1 agonists and the altered images of FDG PET-CT. European Association of Nuclear Medicine (EANM) Annual Congress 2025.