In the setting of ongoing coronavirus disease 2019 vaccination, vaccine-related tracer uptake in locoregional lymph nodes has become a well-known issue in tumor staging by 18F-FDG PET/CT. 68Ga-fibroblast-activation protein inhibitor (FAPI) PET/CT is a new oncologic imaging tool that may overcome this limitation. Methods: We assessed postvaccine head-to-head and same-day 18F-FDG and 68Ga-FAPI-46 PET/CT findings in a series of 11 patients from a large, prospective imaging registry. All patients with documented tracer uptake in locoregional lymph nodes on PET/CT or PET/MRI, after vaccination within 6 wk, were eligible for investigation. Result: Significant visual lymph node uptake adjacent to the injection site was noted in 11 of 11 (100%) patients with 18F-FDG PET/CT, versus 0 of 11 (0%) with 68Ga-FAPI PET/CT. 18F-FDG detected 73% and 68Ga-FAPI PET/CT 94% of all tumor lesions. Conclusion: In this case-series study, 68Ga-FAPI showed its potential to avoid 18F-FDG PET/CT postvaccination pitfalls and presented superior tumor localization.
Keywords: COVID-19; PET; PET/CT; tumor staging; vaccine-related pitfalls.
© 2023 by the Society of Nuclear Medicine and Molecular Imaging.