Accurate preoperative staging with [68Ga]Ga-FAPI PET/CT for patients with oral squamous cell carcinoma: a comparison to 2-[18F]FDG PET/CT

Abstract

Objective: To evaluate the potential value of [⁶⁸Ga]Ga-labelled fibroblast activation protein inhibitor ([⁶⁸Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) in preoperative staging for patients with oral squamous cell carcinoma (OSCC) as compared to 2-[¹⁸F]fluoro-2-deoxy-D-glucose (2-[¹⁸F]FDG) PET/CT.

Methods: Thirty-six treatment-naïve patients with OSCC who underwent 2-[¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI PET/CT for preoperative staging were enrolled. The maximum standardised uptake value (SUV_max) of the primary tumour and suspected cervical metastatic lymph nodes, and the tumour-to-background ratio (TBR) of the primary tumour, were measured. The accuracy of two imaging modalities for preoperative diagnosis of metastatic lymph nodes was analysed. Histopathology served as the standard of reference.

Results: Thirty-seven primary lesions of 36 patients were accurately detected by both [⁶⁸Ga]Ga-FAPI and 2-[¹⁸F]FDG PET/CT. Regarding primary tumours, the SUV_max and TBR of the two imaging modalities in stage T3-T4 were significantly higher than those of stage T1-T2 (all p < 0.05). On the patient analysis, the accuracy for the evaluation of N1-N3 neck status was 52.6% (10/19) for [⁶⁸Ga]Ga-FAPI PET/CT and 57.9% (11/19) for 2-[¹⁸F]FDG PET/CT. Notably, the accuracy for the evaluation of the N0 neck status between [⁶⁸Ga]Ga-FAPI and 2-[¹⁸F]FDG PET/CT was 100% (17/17) and 29% (5/17), respectively. Based on the patient, neck side and neck level, [⁶⁸Ga]Ga-FAPI PET/CT resulted in higher specificity and accuracy in diagnosing metastatic neck lymph nodes than 2-[¹⁸F]FDG PET/CT (all p < 0.05).

Conclusion: [⁶⁸Ga]Ga-FAPI PET/CT is a promising tool for preoperative staging of OSCC, and appears to reduce the false positivity seen with 2-[¹⁸F]FDG PET/CT for the detection of neck lymph node metastases.

Key points: • [⁶⁸Ga]Ga-FAPI PET/CT is a promising tool targeting cancer-associated fibroblasts with comparable diagnostic performance to 2-[¹⁸F]FDG PET/CT for identifying the primary lesions of OSCC. • [⁶⁸Ga]Ga-FAPI PET/CT showed higher specificity and accuracy for the evaluation of neck lymph node metastases of OSCC than 2-[¹⁸F]FDG PET/CT, especially for N0 neck status.

Keywords: 2-[18F]FDG; Neck lymph node metastasis; Oral squamous cell carcinoma; PET/CT; [68Ga]Ga-FAPI.