Head-to-Head Comparison of ⁶⁸Ga-FAPI-46 and ¹⁸F-FDG PET/CT for Evaluation of Head and Neck Squamous Cell Carcinoma: A Single-Center Exploratory Study.

Abstract

⁶⁸Ga-conjugated fibroblast activation protein inhibitor (⁶⁸Ga-FAPI) has become an attractive agent for PET. This study aimed to compare ⁶⁸Ga-FAPI-46 PET/CT with ¹⁸F-FDG PET/CT for detecting primary cancer and metastatic lesions in patients with head and neck squamous cell carcinoma (HNSCC). <b>Methods:</b> Twelve patients and 28 patients with HNSCC underwent ⁶⁸Ga-FAPI-46 and ¹⁸F-FDG PET/CT for initial staging and recurrence detection, respectively. The concordance and diagnostic accuracy of both tracers were analyzed. Semiquantitative parameters, including SUV_max, SUV_mean, and tumor-to-background ratio, were compared. Fibroblast activation protein (FAP) expression tumor volume and total lesion FAP expression of ⁶⁸Ga-FAPI-46 were compared with metabolic tumor volume and total lesion glycolysis of ¹⁸F-FDG, respectively. Differences between semiquantitative parameters were analyzed using paired <i>t</i> testing. <b>Results:</b>⁶⁸Ga-FAPI-46 PET/CT was 83.3% and 96.4% concordant with ¹⁸F-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 (<i>P</i> < 0.05), but no significant differences were observed for the other parameters. <b>Conclusion:</b>⁶⁸Ga-FAPI-46 PET/CT showed good concordance with, and comparable diagnostic performance to, ¹⁸F-FDG PET/CT for initial staging and recurrence detection in HNSCC patients.