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.