Novel <sup>68</sup>Ga-FAPI PET/CT Offers Oncologic Staging Without COVID-19 Vaccine-Related Pitfalls.

Demmert, Tristan T; Maric, Ines; Pomykala, Kelsey L; Lueckerath, Katharina; Siveke, Jens; Schaarschmidt, Benedikt M; Hamacher, Rainer; Herrmann, Ken et al. · J Nucl Med · 2023

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Abstract

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 <sup>18</sup>F-FDG PET/CT. <sup>68</sup>Ga-fibroblast-activation protein inhibitor (FAPI) PET/CT is a new oncologic imaging tool that may overcome this limitation. <b>Methods:</b> We assessed postvaccine head-to-head and same-day <sup>18</sup>F-FDG and <sup>68</sup>Ga-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. <b>Result:</b> Significant visual lymph node uptake adjacent to the injection site was noted in 11 of 11 (100%) patients with <sup>18</sup>F-FDG PET/CT, versus 0 of 11 (0%) with <sup>68</sup>Ga-FAPI PET/CT. <sup>18</sup>F-FDG detected 73% and <sup>68</sup>Ga-FAPI PET/CT 94% of all tumor lesions. <b>Conclusion:</b> In this case-series study, <sup>68</sup>Ga-FAPI showed its potential to avoid <sup>18</sup>F-FDG PET/CT postvaccination pitfalls and presented superior tumor localization.

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