Clinical utility of [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 [Ga]Ga-labeled fibroblast activation protein inhibitor ([Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) relative to [F]-fluorodeoxyglucose ([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 [F]FDG and [Ga]Ga-FAPI PET/CT between October 2019 and November 2020 were included. The radiotracer uptake and clinical staging/restaging performances of [F]FDG and [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, [Ga]Ga-FAPI PET/CT showed higher radiotracer uptake than [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 [F]FDG-based TNM stage, the [Ga]Ga-FAPI-based TNM stage was upgraded in ten patients (26%), resulting in management changes in seven patients (18%). Compared with MRI, [Ga]Ga-FAPI PET/CT upgraded and underestimated the T stage in four and two patients, respectively. In post-treatment patients, [Ga]Ga-FAPI PET/CT yielded more true-positive findings than [F]FDG PET/CT in detecting local recurrence.

CONCLUSION

[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 [Ga]Ga-FAPI PET/CT may be a supplement to MRI for T staging and radiotherapy planning.