Dual-tracer PET/CT protocol with [18F]FDG and [68Ga]Ga-FAPI-46 outperforms single-tracer PET/CT with [18F]FDG in different cancer types, resulting in larger functional and gross tumor volume
Simone Wegen, Jasmin Weindler, Conrad‐Amadeus Voltin, Lutz van Heek, Klaus Schomäcker, Thomas Fischer, Simone Marnitz, Carsten Kobe, Alexander Drzezga, Katrin Sabine Roth
Abstract
Abstract Purpose Fibroblast activation protein (FAP) detected by positron-emission tomography (PET) using fibroblast activation protein inhibitor (FAPI) appears to be a promising target for cancer imaging, staging, and therapy, providing added value and strength as a complement to [ 18 F]fluorodeoxyglucose (FDG) in cancer imaging. We recently introduced a combined single-session/dual-tracer protocol with [ 18 F]FDG and [ 68 Ga]Ga-FAPI for cancer imaging and staging. Malignant tissue visualization and target-to-background uptake ratios (TBRs) as well as functional tumor volume (FTV) and gross tumor volume (GTV) were assessed in the present study with single-tracer [ 18 F]FDG PET/computed tomography (CT) and with dual-tracer [ 18 F]FDG&[ 68 Ga]Ga-FAPI-46 PET/CT. Methods A total of 19 patients with head and neck and gastrointestinal cancers received initial [ 18 F]FDG-PET/CT followed by dual-tracer PET/CT after additional injection of [ 68 Ga]Ga-FAPI-46 during the same medical appointment (on average 13.9 ± 12.3 min after injection of [ 18 F]FDG). Two readers visually compared detection rate of malignant tissue, TBR, FTV, and GTV for tumor and metastatic tissue in single- and dual-tracer PET/CT. Results The diagnostic performance of dual-tracer compared to single-tracer PET/CT was equal in 13 patients and superior in 6 patients. The mean TBRs of tumors and metastases in dual-tracer PET/CTs were mostly higher compared to single-tracer PET/CT using maximal count rates (CRmax). GTV and FTV were significantly larger when measured on dual-tracer compared to single-tracer PET/CT. Conclusion Dual-tracer PET/CT with [ 18 F]FDG and [ 68 Ga]Ga-FAPI-46 showed better visualization due to a generally higher TBR and larger FTV and GTV compared to [ 18 F]FDG-PET/CT in several tumor entities, suggesting that [ 68 Ga]Ga-FAPI-46 provides added value in pretherapeutic staging.