Tristan T Demmert 1, Ines Maric 1, Kelsey L Pomykala 2, Katharina Lueckerath 1, Jens Siveke 3, Benedikt M Schaarschmidt 4, Rainer Hamacher 3, Ken Herrmann 1, Wolfgang P Fendler 1

Abstract

In the setting of ongoing SARS-CoV-2 vaccination, vaccine-related tracer uptake in locoregional lymph nodes has become a well-known issue in tumor staging by 18F-FDG PET/CT. 68Ga-FAPI PET/CT is a new oncologic imaging tool that may overcome this limitation.

Methods: We assessed post-vaccine, 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, following vaccination within 6 weeks, were eligible for investigation.

Result: Significant visual lymph node uptake adjacent to the injection site was noted in 11/11 (100%) patients with 18F-FDG PET/CT versus 0/11 (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 post-vaccination pitfalls and presented superior tumor localization.