Oncologic Staging with ⁶⁸Ga-FAPI PET/CT Demonstrates a Lower Rate of Nonspecific Lymph Node Findings Than ¹⁸F-FDG PET/CT.

Abstract

Nonspecific lymph node uptake on ¹⁸F-FDG PET/CT imaging is a significant pitfall for tumor staging. Fibroblast activation protein α expression on cancer-associated fibroblasts and some tumor cells is less sensitive to acute inflammatory stimuli, and fibroblast activation protein-directed PET may overcome this limitation. <b>Methods:</b> Eighteen patients from our prospective observational study underwent ¹⁸F-FDG and ⁶⁸Ga fibroblast activation protein inhibitor (FAPI) PET/CT scans within a median of 2 d (range, 0-22 d). Lymph nodes were assessed on histopathology and compared with SUV measurements. <b>Results:</b> On a per-patient basis, lymph nodes were rated malignant in 10 (56%) versus 7 (39%) patients by ¹⁸F-FDG PET/CT versus ⁶⁸Ga-FAPI PET/CT scans, respectively, with a respective accuracy of 55% versus 94% for true lymph node metastases. Five of 6 (83%) false-positive nodes on the ¹⁸F-FDG PET/CT scans were rated true negative by the ⁶⁸Ga-FAPI PET/CT scans. On a per-lesion basis, tumor detection rates were similar (85/89 lesions, 96%). <b>Conclusion:</b> ⁶⁸Ga-FAPI PET/CT imaging demonstrated higher accuracy for true nodal involvement and therefore has the potential to replace ¹⁸F-FDG PET/CT imaging for cancer staging.