Reston, VA—A novel imaging agent, 68Ga-FAPI, can reduce the number of false-positive PET/CT findings among cancer patients recently vaccinated for COVID-19. New research published ahead of print in The Journal of Nuclear Medicine shows that 68Ga-FAPI imaging offers superior lesion detection without vaccine-related tracer uptake in locoregional lymph nodes that is common with 18F-FDG imaging. This can help to prevent costly follow-up and false management decisions for cancer patients.
One side effect of the COVID-19 vaccine is that 18F-FDG (the most commonly used PET imaging agent) is taken up by immune cells responding to the mRNA inflammatory stimulus caused by the vaccine. This is known as a reactive uptake and does not always indicate that a tumor is present.
“This observation is concerning as vulnerable groups, such as oncologic 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 findings on 18F-FDG PET due to reactive uptake may trigger false management decisions.”
To find a way to avoid these false positives, researchers compared two radiotracers, 68Ga-FAPI and 18F-FDG. Using a large prospective imaging registry, researchers investigated 11 oncologic patients who had received a COVID-19 vaccination within six weeks, had 68Ga-FAPI and 18F-FDG imaging on the same day, and had documentation of tracer uptake in locoregional lymph nodes. Visual readings of the images were performed by two nuclear medicine physicians.
Significant lymph node uptake adjacent to the injection site was noted in 11/11 patients with 18F-FDG PET/CT versus 0/11 with 68Ga-FAPI PET/CT. In addition, 18F-FDG detected 73 percent of tumor lesions, while 68Ga-FAPI detected 94 percent of all tumor lesions.
“In patients with suspected tumors in the axillary region, a costly follow-up was often recommended to avoid incorrect patient treatment. According to our results, this could have been prevented by using 68Ga-FAPI, which would have allowed higher tumor detection at the same time,” noted Demmert. “Considering that further booster vaccinations are expected, 68Ga-FAPI could show its potential in avoiding vaccine-related misinterpretations on PET/CT while providing equivalent tumor detection.”
This study was made available online in November 2022.
The authors of “Novel 68Ga-FAPI PET/CT offers oncologic staging without COVID-19 vaccine-related pitfalls” include Tristan T. Demmert, Ines Maric, Katharina Lueckerath, Ken Herrmann, and Wolfgang P. Fendler, Department of Nuclear Medicine, West German Cancer Center, University of Duisburg-Essen, Essen, Germany, and German Cancer Consortium (DKTK), Partner Site University Hospital Essen, and Germany Cancer Research Center (DKFZ), Essen, Germany; Kelsey L. Pomykala, Institute for AI in Medicine (IKIM), University Medicine, Essen, Germany; Jens Siveke, German Cancer Consortium (DKTK), Partner Site University Hospital Essen, and Germany Cancer Research Center (DKFZ), Essen, Germany, and Bridge Institute of Experimental Tumor Therapy, West German Cancer Center, University Hospital Essen, University of Duisburg-Essen, Essen, Germany; Benedikt M. Schaarschmidt, Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany; and Rainer Hamacher, German Cancer Consortium (DKTK), Partner Site University Hospital Essen, and Germany Cancer Research Center (DKFZ), Essen, Germany, and Department of Medical Oncology, West German Cancer Center, University Hospital Essen, Essen, Germany.
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Journal of Nuclear Medicine
Novel 68Ga-FAPI PET/CT offers oncologic staging without COVID-19 vaccine-related pitfalls
Katharina Lueckerath reports fees from SOFIE Bioscience (consultant) and Enlaza Therapeutics (consultant). Rainer Hamacher is supported by Clinician Scientist Program of the University Medicine Essen Clinician Scientist Academy (UMEA) sponsored by faculty of medicine and Deutsche Forschungsgemeinschaft (DFG) and has received travel grants from Lilly, Novartis and PharmaMar as well as fees from Lilly and PharmaMar. Jens T. Siveke received honoraria as consultant or for continuing medical education presentations from AstraZeneca, Bayer, Bristol-Myers Squibb, Eisbach Bio, Immunocore, Novartis, Roche/Genentech, Servier; his institution receives research funding from Bristol-Myers Squibb, Celgene, Eisbach Bio, Roche/Genentech; he holds ownership and serves on the Board of Directors of Pharma15, all outside the submitted work. Benedikt M. Schaarschmidt received a research grant from PharmaCept for an undergoing investigator-initiated study not related to this paper. Ken Herrmann reports personal fees from Bayer, personal fees and other from Sofie Biosciences, personal fees from SIRTEX, non-financial support from ABX, personal fees from Adacap, personal fees from Curium, personal fees from Endocyte, grants and personal fees from BTG, personal fees from IPSEN, personal fees from Siemens Healthineers, personal fees from GE Healthcare, personal fees from Amgen, personal fees from Novartis, personal fees from ymabs, personal fees from Aktis Oncology, personal fees from Theragnostics, personal fees from Pharma15, outside the submitted work. Wolfgang P. Fendler reports fees from SOFIE Bioscience (research funding), Janssen (consultant, speakers bureau), Calyx (consultant), Bayer (consultant, speakers bureau, research funding), Parexel (image review) and AAA (speakers bureau) outside of the submitted work. All disclosure were outside of the submitted work.