Head-to-Head Comparison of Ga-FAPI-46 and F-FDG PET/CT for Evaluation of Head and Neck Squamous Cell Carcinoma: A Single-Center Exploratory Study.

Ga-conjugated fibroblast activation protein inhibitor (Ga-FAPI) has become an attractive agent for PET. This study aimed to compare Ga-FAPI-46 PET/CT with F-FDG PET/CT for detecting primary cancer and metastatic lesions in patients with head and neck squamous cell carcinoma (HNSCC). Twelve patients and 28 patients with HNSCC underwent Ga-FAPI-46 and F-FDG PET/CT for initial staging and recurrence detection, respectively. The concordance and diagnostic accuracy of both tracers were analyzed. Semiquantitative parameters, including SUV, SUV, and tumor-to-background ratio, were compared. Fibroblast activation protein (FAP) expression tumor volume and total lesion FAP expression of Ga-FAPI-46 were compared with metabolic tumor volume and total lesion glycolysis of F-FDG, respectively. Differences between semiquantitative parameters were analyzed using paired testing. Ga-FAPI-46 PET/CT was 83.3% and 96.4% concordant with F-FDG PET/CT for initial staging and recurrence detection, respectively. Eighteen lesions had histopathologic validation, and both tracers displayed 100% sensitivity, 50% specificity, and 94.4% accuracy for lesion-based analysis. FAP expression tumor volume was greater than metabolic tumor volume ( < 0.05), but no significant differences were observed for the other parameters. Ga-FAPI-46 PET/CT showed good concordance with, and comparable diagnostic performance to, F-FDG PET/CT for initial staging and recurrence detection in HNSCC patients.