Clinical utility of [⁶⁸Ga]Ga-labeled fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography for primary staging and recurrence detection in nasopharyngeal carcinoma.

Abstract

This study aimed to explore the clinical utility of [⁶⁸Ga]Ga-labeled fibroblast activation protein inhibitor ([⁶⁸Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) relative to [¹⁸F]-fluorodeoxyglucose ([¹⁸F]FDG) PET/CT and magnetic resonance imaging (MRI) for primary staging and recurrence detection in nasopharyngeal carcinoma (NPC). This retrospective analysis utilized a sub-cohort of patients from a previously acquired database. Patients with NPC who underwent [¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI PET/CT between October 2019 and November 2020 were included. The radiotracer uptake and clinical staging/restaging performances of [¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI PET/CT were compared. Forty-five participants (39 for initial assessment, 6 for recurrence detection) were included. In treatment-naïve participants, [⁶⁸Ga]Ga-FAPI PET/CT showed higher radiotracer uptake than [¹⁸F]FDG PET/CT in primary tumors (16.18 vs. 10.11, P < 0.001), regional lymph nodes (11.42 vs. 7.37, P < 0.001), and bone and visceral metastases (6.94 vs. 3.11, P < 0.001). Compared with the [¹⁸F]FDG-based TNM stage, the [⁶⁸Ga]Ga-FAPI-based TNM stage was upgraded in ten patients (26%), resulting in management changes in seven patients (18%). Compared with MRI, [⁶⁸Ga]Ga-FAPI PET/CT upgraded and underestimated the T stage in four and two patients, respectively. In post-treatment patients, [⁶⁸Ga]Ga-FAPI PET/CT yielded more true-positive findings than [¹⁸F]FDG PET/CT in detecting local recurrence. [⁶⁸Ga]Ga-FAPI PET/CT is a promising imaging modality for the diagnosis of primary and metastatic NPC. The exact tumor geographic imaging obtained through [⁶⁸Ga]Ga-FAPI PET/CT may be a supplement to MRI for T staging and radiotherapy planning.