Low false-positive lymph nodes for 18 F-fibroblast activation protein inhibitors PET/computed tomography in preoperative staging of patients with nonsmall cell lung cancer.

Objective: This study aimed to evaluate the diagnostic accuracy of 18 F-fibroblast activation protein inhibitor (FAPI) PET/computed tomography (CT) in identifying primary tumors and mediastinal lymph node metastases in nonsmall cell lung cancer (NSCLC), with histopathological findings serving as the reference standard.

Methods: Nineteen patients underwent preoperative 18 F-FAPI PET/CT and subsequent surgery; of these, 13 also underwent 18 F-fluorodeoxyglucose (FDG) PET/CT within 1 week. The diagnostic accuracy of primary tumors and lymph node metastases was evaluated for both modalities. Semiquantitative parameters, including maximum standardized uptake values (SUV max ) and target-to-background ratios (TBRs), for both primary tumors and lymph node metastases were assessed for both modalities.

Results: For primary tumors, 18 of 19 (94.7%) showed positive results on 18 F-FAPI PET/CT scans. In 13 patients who also underwent 18 F-FDG PET/CT, 18 F-FAPI PET/CT demonstrated a higher detection rate compared with 18 F-FDG PET/CT (100% vs. 69.1%). The overall accuracy of lymph node assessment with 18 F-FAPI PET/CT (95.9-97.1%) was significantly higher compared to 18 F-FDG PET/CT (51.0%). Malignant lymph nodes exhibited significantly higher SUV max and TBR on 18 F-FAPI scans (SUV max : 7.0 vs. 0.9, P  < 0.001; TBR muscle : 5.0 vs. 0.8, P  < 0.001) than on 18 F-FDG scans (SUV max : 3.9 vs. 1.8, P  = 0.01), except for the liver TBR on 18 F-FDG scans (TBR liver : 1.8 vs. 1.0, P  = 0.055).

Conclusion: 18 F-FAPI could be utilized in the preoperative staging of NSCLC to mitigate the incidence of false positives associated with 18 F-FDG, due to its higher accuracy in identifying mediastinal lymph node metastasis.