Head-to-head intra-individual comparison of biodistribution and tumor uptake of 68Ga-FAPI and 18F-FDG PET/CT in cancer patients
Frederik L. Giesel, Clemens Kratochwil, Joel Schlittenhardt, Katharina Dendl, Matthias Eiber, Fabian Staudinger, Lukas Kessler, Wolfgang P. Fendler, Thomas Lindner, Stefan A. Koerber, Jens Cardinale, D Sennung, Manuel Roehrich, Jürgen Debus, Mike Sathekge, Uwe Haberkorn, Jérémie Calais, Sebastian E. Serfling, Andreas L. Buck
Abstract
Abstract Purpose FAPI ligands (fibroblast activation protein inhibitor), a novel class of radiotracers for PET/CT imaging, demonstrated in previous studies rapid and high tumor uptake. The purpose of this study is the head-to-head intra-individual comparison of 68 Ga-FAPI versus standard-of-care 18 F-FDG in PET/CT in organ biodistribution and tumor uptake in patients with various cancers. Material and Methods This international retrospective multicenter analysis included PET/CT data from 71 patients from 6 centers who underwent both 68 Ga-FAPI and 18 F-FDG PET/CT within a median time interval of 10 days (range 1–89 days). Volumes of interest (VOIs) were manually drawn in normal organs and tumor lesions to quantify tracer uptake by SUVmax and SUVmean. Furthermore, tumor-to-background ratios (TBR) were generated (SUVmax tumor/ SUVmax organ). Results A total of 71 patients were studied of, which 28 were female and 43 male (median age 60). In 41 of 71 patients, the primary tumor was present. Forty-three of 71 patients exhibited 162 metastatic lesions. 68 Ga-FAPI uptake in primary tumors and metastases was comparable to 18 F-FDG in most cases. The SUVmax was significantly lower for 68 Ga-FAPI than 18 F-FDG in background tissues such as the brain, oral mucosa, myocardium, blood pool, liver, pancreas, and colon. Thus, 68 Ga-FAPI TBRs were significantly higher than 18 F-FDG TBRs in some sites, including liver and bone metastases. Conclusion Quantitative tumor uptake is comparable between 68 Ga-FAPI and 18 F-FDG, but lower background uptake in most normal organs results in equal or higher TBRs for 68 Ga-FAPI. Thus, 68 Ga-FAPI PET/CT may yield improved diagnostic information in various cancers and especially in tumor locations with high physiological 18 F-FDG uptake.