Head-to-head comparison of [F]FAPI-42 and [F]FDG PET/CT in the evaluation of laryngeal squamous cell carcinoma.

Purpose: To investigate the clinical utility of [F]FAPI-42 PET/CT relative to [F]FDG PET/CT for tumor detection and staging in laryngeal squamous cell carcinoma (LSCC) patients.

Methods: Patients with pathologically proven LSCC were prospectively enrolled. All patients underwent [F]FDG and [F]FAPI-42 PET/CT within 1 week. Primary tumor and lymph node showed by [F]FDG and [F]FAPI-42 PET/CT were compared by SUVmax and visual assessment. The primary tumor volumes derived from [F]FDG PET, [F]FAPI-42 PET, and contrast-enhanced CT were also compared.

Results: Twenty-one patients were included from January to October 2024. [F]FAPI-42 PET/CT has a higher positive detection rate of primary tumor than [F]FDG (100% vs. 85.7%). For visual assessment of primary tumor invasion, [F]FAPI-42 was superior to [F]FDG in 9 of 21 patients (42.9%) and inferior to [F]FDG in 1 patient (4.8%), which was confirmed by pathology. The diagnostic efficacy of [F]FAPI-42 PET/CT for T staging was higher than that of [F]FDG PET/CT (95.3% vs. 57.1%, P = 0.021). [F]FAPI-42 led to downstaging of N stage in 4 of 21 patients (19.0%) relative to [F]FDG PET/CT, which was consistent with pathology. Compared with [F]FDG, [F]FAPI-42 PET/CT changed overall staging in 10 of 21 patients, with 5 patients being up-staged and 5 down-staged. When 35% SUVmax of [F]FDG or 40% SUVmax of [F]FAPI-42 was used as a threshold for delineating tumor volume, it was highly consistent with contrast-enhanced CT.

Conclusion: [F]FAPI-42 outperforms [F]FDG in the tumor detection, staging, and the delineation of primary tumor, indicating that [F]FAPI-42 PET/CT may serve as a promising imaging modality for detecting and staging patients with LSCC. Its value regarding distant metastases evaluation requires further investigation.

Trial Registration: NCT06304155. https://clinicaltrials.gov/study/NCT06304155 .