Qin_2021_Eur.J.Nucl.Med.Mol.Imaging_48_3228

PURPOSE: To conduct a head-to-head comparison of the diagnostic ability of (68)Ga-DOTA-FAPI-04 ((68)Ga-FAPI) and (18)F-FDG PET/MR in nasopharyngeal carcinoma (NPC) patients. METHODS: Patients diagnosed with NPC were prospectively enrolled. All patients underwent head-and-neck (68)Ga-FAPI PET/MR and (18)F-FDG PET/MR within 1 week. Primary tumor, lymph node numbers, and tracer uptake were compared by SUVmax and visual evaluation. The primary tumor volumes derived from (68)Ga-FAPI, (18)F-FDG PET, and MRI were also compared. RESULTS: Fifteen patients were enrolled from June to August 2020. Both (68)Ga-FAPI and (18)F-FDG PET had 100% detection rate of the primary tumor. The (68)Ga-FAPI SUVmax of primary tumors (13.87 +/- 5.13) was lower than that of (18)F-FDG (17.73 +/- 6.84), but the difference was not significant (p = 0.078). Compared with (18)F-FDG, (68)Ga-FAPI PET improved the delineation of skull-base invasion in eight out of eight patients and intracranial invasion in four out of four patients. When 25%SUVmax of (68)Ga-FAPI or 20%SUVmax of (18)F-FDG was utilized as a threshold for determining tumor volume, it was highly consistent with MRI. (18)F-FDG PET detected much more positive lymph nodes than (68)Ga-FAPI (100 vs 48). The SUVmax of 48 paired lymph nodes was significantly lower on (68)Ga-FAPI than (18)F-FDG (8.67 +/- 3.88 vs 11.79 +/- 6.17, p < 0.001). Additionally, (68)Ga-FAPI further detected four highly suspected small, distant metastases in three patients. Compared with (18)F-FDG, (68)Ga-FAPI changed overall staging in six of fifteen patients, with three patients being up-staged, and three down-staged. CONCLUSION: (68)Ga-FAPI outperforms (18)F-FDG in delineating the primary tumor and detecting suspected distant metastases, particularly in the evaluation of skull-base and intracranial invasion, suggesting (68)Ga-FAPI hybrid PET/MR has the potential to serve as a single-step staging modality for patients with NPC. However, its value regarding lymph node and distant metastases evaluation needs further study. TRIAL REGISTRATION: NCT04554719. Registered September 8, 2020 - retrospectively registered, http://clinicaltrails.gov/show/NCT04554719.