[ ⁶⁸ Ga]Ga-FAPI04 Outperforms [ ¹⁸ F]FDG PET/CT for Detecting Nodal Metastasis of Head and Neck Squamous Cell Carcinoma: A Single-Center Experience

This study assesses fibroblast activated protein inhibitor (FAPI) targeted PET/CT imaging against [¹⁸F]FDG PET/CT (FDG PET) for detecting nodal involvement in head and neck squamous cell carcinoma (HNSCC), intending to improve diagnostic precision for metastatic lymph nodes and lay the groundwork for future investigations. <b><i>Methods:</i></b> Patients diagnosed with HNSCC were retrospectively enrolled. All patients underwent [⁶⁸Ga]Ga-FAPI04 PET/CT (FAPI PET) and FDG PET within 6 d. Primary tumor, lymph nodes, and tracer uptake were visually and quantitatively compared. The metastatic lymph nodes were evaluated using patient-and lesion-based analyses, with biopsy or postoperative histopathological examination as the reference. <b><i>Results:</i></b> The cohort includes 24 patients (17 men, 7 women; mean age 60 ± 11.8 years) who underwent FDG and FAPI PET for preoperative diagnostic workup or restaging due to known recurrence of HNSCC. Lesions included 24 primary tumors, 54 cervical lymph nodes, and 5 metastases. Primary tumors exhibited significant uptake on both PET modalities (median maximum standardized uptake value [SUV_max]: FDG 19.4 ± 11.6, FAPI 16.9 ± 4.6), with no statistically significant difference (<i>p</i> > 0.5). For lymph nodes, FAPI and FDG PET showed median SUV_max of 9.18 ± 6.77 and 9.67 ± 6.5, respectively. The patient-based analysis found FDG PET sensitivity at 88.2% and FAPI PET at 94.1%, with FAPI PET specificity significantly higher (85.7% vs. 42.8% for FDG PET). Lesion-based analysis revealed FAPI PET sensitivity and specificity at 84.2% and 93.7%, respectively, contrasting FDG PET's at 81.5% and 25%, respectively. <b><i>Conclusion:</i></b> This study underscores the efficacy of FAPI PET in detecting primary tumors in HNSCC. Furthermore, FAPI PET shows improved specificity over FDG PET for metastatic lymph nodes advocating further investigations for integrating FAPI PET into HNSCC clinical protocols for its enhanced precision in detecting metastatic lymph nodes.