Superiority of Ga-68-FAPI-46 over F-18-FDG PET/CT in patients with solitary fibrous tumors (SFT)

Ziel/Aim SFTs are rare mesenchymal tumors frequently diagnosed late due to delayed occurrence of symptoms. Localized tumors are mostly treated by resection, while there is no effective standard treatment for advanced, metastatic stages. Hence, accurate imaging is essential, especially due to detection limits of current imaging modalities. Therefore, we aim to assess accuracy and impact on management of Ga-68-FAPI-46 PET.

Methodik/Methods 10 patients with advanced SFTs who received clinical Ga-68-FAPI-46 and F-18-FDG PET/CTs between July 2020 and February 2022 were enrolled in an observational study and retrospectively reviewed. For detection efficacy, two blinded nuclear medicine physicians and one radiologist performed a lesion-based analysis independently. Disagreement was resolved by joint consensus read. Standard of reference were conventional CT and/or clinical/imaging follow-up. A lesion-based analysis of SUV_max/SUV_mean was performed and Tumor-to-Background ratios (TBRs) (liver, blood pool, muscle) were compared using Wilcoxon-Test. Change in management was determined by questionnaires sent to the treating physician after imaging was performed. P<0.05 was considered statistically significant.

Ergebnisse/Results 227 lesions were detected across all imaging modalities. On a per-lesion basis, detection efficacy for Ga-68-FAPI-46 PET vs. F-18-FDG PET vs. CT was 100% vs. 67.4% vs. 84.6%. Ga-68-FAPI-46 demonstrated significantly higher SUV_max/SUV_mean (average (SD): 21.7 (24)/12.9 (14.8) vs. 4.2 (2.6)/2.5 (1.5), both p<0.05) and TBRs (average (SD): TBRblood pool: 16.0 (16.3) vs. 2.7 (2.0); TBRliver: 25.7 (29.7) vs. 2.2 (1.5); TBRmuscle: 14.7 (13.7) vs. 6.6 (4.7); all p<0.05) when compared with F-18-FDG PET. Major change in management, i.e. additional surgery, was noted in 2/10 patients (20%).

Schlussfolgerungen/Conclusions In conclusion, Ga-68-FAPI-46 demonstrated higher tumor uptake which translated into superior detection efficacy and change in management when compared with F-18-FDG and CT. Ga-68-FAPI-46 PET for SFT is further assessed in an ongoing prospective trial (NCT05160051).

Publication History

Article published online:
30 March 2023