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

Purpose: This study aimed to explore the clinical utility of [ ⁶⁸ Ga]Ga-labeled fibroblast activation protein inhibitor ([ ⁶⁸ Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) relative to [ ¹⁸ F]-fluorodeoxyglucose ([ ¹⁸ F]FDG) PET/CT and magnetic resonance imaging (MRI) for primary staging and recurrence detection in nasopharyngeal carcinoma (NPC).
Methods: This retrospective analysis utilized a sub-cohort of patients from a previously acquired database. Patients with NPC who underwent [ ¹⁸ F]FDG and [ ⁶⁸ Ga]Ga-FAPI PET/CT between October 2019 and November 2020 were included. The radiotracer uptake and clinical staging/restaging performances of [ ¹⁸ F]FDG and [ ⁶⁸ Ga]Ga-FAPI PET/CT were compared.
Results: Forty-five participants (39 for initial assessment, 6 for recurrence detection) were included. In treatment-naïve participants, [ ⁶⁸ Ga]Ga-FAPI PET/CT showed higher radiotracer uptake than [ ¹⁸ F]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 [ ¹⁸ F]FDG-based TNM stage, the [ ⁶⁸ Ga]Ga-FAPI-based TNM stage was upgraded in ten patients (26%), resulting in management changes in seven patients (18%). Compared with MRI, [ ⁶⁸ Ga]Ga-FAPI PET/CT upgraded and underestimated the T stage in four and two patients, respectively. In post-treatment patients, [ ⁶⁸ Ga]Ga-FAPI PET/CT yielded more true-positive findings than [ ¹⁸ F]FDG PET/CT in detecting local recurrence.
Conclusion: [ ⁶⁸ Ga]Ga-FAPI PET/CT is a promising imaging modality for the diagnosis of primary and metastatic NPC. The exact tumor geographic imaging obtained through [ ⁶⁸ Ga]Ga-FAPI PET/CT may be a supplement to MRI for T staging and radiotherapy planning.
(© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)