[18F]F-FAPI PET/CT is superior to [18F]F-FDG PET/CT for lymph node staging in lung cancer: a pathologically validated study.

PURPOSE: Accurate lymph node staging in lung cancer remains challenging. This study evaluates the diagnostic efficacy of fibroblast activation protein inhibitor (FAPI) versus fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) using histopathology as the reference standard.

METHODS

Thirty-two lung cancer patients with FDG-positive lymph nodes underwent [¹⁸F]F-FAPI PET/CT. Pathological confirmation of 71 lymph nodes (23 metastatic, 48 benign) was obtained via surgery or endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). Diagnostic efficacy was evaluated on both lymph node-based and patient-based, including maximum standardized uptake value (SUVmax), tumor-to-background ratio (TBR), sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) .

RESULTS

Metastatic lymph nodes showed significantly higher FAPI uptake vs. benign lymph nodes [SUVmax: (13.6 ± 9.6) vs. (2.7 ± 1.9)]; p < 0.001). Receiver operating characteristic (ROC) analysis showed a significantly larger area under the curve (AUC) for [18F]F-FAPI compared to [18F]F-FDG [AUC 0.98 (95% CI 0.95-1.0) vs. AUC 0.78 (0.65-0.89), (p < 0.001)]. In this cohort of patients with FDG-positive lymph nodes, [18F]F-FAPI presented greater lymph node detection sensitivity, specificity, accuracy, PPV and NPV than [18F]F-FDG (100% vs. 100%, 91.7% vs. 16.7%, 97.0% vs. 43.9%, 85.2% vs. 36.5% and 100% vs. 100% respectively). When the cut-off value of SUVmax is greater than 5.3, [18F]F-FAPI can correctly identify all 23 metastatic lymph nodes with much lower false positive rate than [18F]F-FDG (0% vs. 83.3%). [18F]F-FAPI shows higher lymph node staging accuracy than [18F]F-FDG [93.8% (30/32) vs. 43.8% (14/32)], led to downstaging in 15 patients. In 42.9% (9/21) of patients who underwent EBUS-TBNA, the procedure could have been safely avoided.

CONCLUSION

[18F]F-FAPI PET/CT is a promising tool for lymph node staging of lung cancer, offering higher specificity and reduced false positives, with potential to optimize invasive staging procedures.