Novel PET radiotracer reduces number of false positive cancer results after COVID-19 vaccination

Novel PET radiotracer reduces number of false positive cancer results after COVID-19 vaccination

The new 68Ga-FAPI PET/CT offers cancer staging without the pitfalls of the COVID-19 vaccine. Credit: Tristan T. Demmert et al., Department of Nuclear Medicine, University Hospital Essen.

A new imaging agent, 68Ga-FAPI, may reduce the number of false positive PET/CT results among cancer patients recently vaccinated for COVID-19. New research published ahead of print in Journal of Nuclear Medicine shows that 68Ga-FAPI imaging offers superior lesion detection without vaccine-related tracer uptake in locoregional lymph nodes which is common with 18F-FDG imaging. This can help prevent costly follow-ups and false management decisions for cancer patients.

One side effect of the COVID-19 vaccine is this 18fFDG (the most commonly used PET imaging agent) is taken up by immune cells that respond to the inflammatory mRNA stimulus caused by the vaccine. This is known as reactive absorption and does not always indicate the presence of a tumor.

“This observation is concerning as vulnerable groups, such as cancer patients, undergo both regular COVID-19 booster shots and medical imaging,” said Tristan T. Demmert, researcher in the Department of Nuclear Medicine at Essen University Hospital in Essen, Germany. “False positive results on 18F-FDG PET due to reactive absorption can trigger false management decisions.”

To find a way to avoid these false positives, the researchers compared two radiotracers, 68Ga-FAPI e 18F-FDG. Using a large prospective imaging registry, the researchers studied 11 cancer patients who had received a COVID-19 vaccination within six weeks, had 68Ga-FAPI e 18F-FDG imaging on the same day and documentation of tracer uptake in locoregional lymph nodes. Visual readings of the images were performed by two nuclear medicine physicians.

In 11/11 patients with 18F-FDG PET/CT versus 0/11 con 68Ga-FAPI PET/TAC. Moreover, 18F-FDG detected 73% of tumor lesions, while 68Ga-FAPI detected 94% of all tumor lesions.

“In patients with suspected tumors in the axillary region, an expensive follow-up was often recommended to avoid mistreatment of the patient. According to our results, this could have been avoided by using 68Ga-FAPI, which would have enabled increased tumor detection at the same time,” Demmert noted. “Considering that additional booster vaccinations are planned, 68Ga-FAPI could show its potential in avoiding vaccine-related misinterpretations on PET/CT while providing equivalent tumor detection.”

More information:
Tristan T. Demmert et al, Novel68Ga-FAPI PET/CT offers cancer staging without COVID-19 vaccine pitfalls, Journal of Nuclear Medicine (2022). DOI: 10.2967/jnumed.122.264872

Provided by the Society of Nuclear Medicine and Molecular Imaging

Quote: New PET radiotracer reduces number of false positive cancer results after COVID-19 vaccination (2023, Jan 11) retrieved Jan 11, 2023 from -false-positive-cancer-covid-.html

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