A pilot Study of Pretreatment 68GaGa-FAPI-04 PET/CT: Correlation of Imaging Parameters with Prognosis and FAP Expression in Soft Tissue Sarcoma

Abstract Objectives This study was developed with the primary goal of assessing any potential correlations between 68GaGa -FAPI-04 PET/CT-derived parameters and the overall and progression-free survival (OS and PFS) of patients with soft tissue sarcoma (STS). The association between sarcomatous lesional uptake and FAP immunohistochemistry (IHC) results was also examined. Methods Patients with a primary STS diagnosis who underwent 68GaGa-FAPI-04 PET/CT were retrospectively evaluated. Basic information included age, gender, tumor size location, necrosis volume, and 68GaGa-FAPI-04 PET/CT-based parameters included maximum tumor standardized uptake value (SUVmax), FAPI-avid tumor volume (FTV), and total lesion FAP expression (TLF). Prognostic outcomes were analyzed using Kaplan-Meier curves and Cox regression. Spearman’s correlation was used to examine the association between 68GaGa-FAPI-04 uptake and FAP expression. Results Survival analyses included 22 patients, of whom 10 underwent FAP IHC staining. A significant association was observed between FAP levels and SUVmax for these STS patients (r = 0.88, P 0.001). In univariate analyses, FTV and TLF were both significantly correlated with OS and PFS (P 0.05). SUVmax, in contrast, was only correlated with patient OS. FTV and TLF values were established as significant independent predictors of PFS (HR = 4.15, P = 0.01) and OS (HR = 4.12, P = 0.02). In addition, a roughly 3-fold greater risk of progression was also noted for patients with a tumor necrosis volume exceeding 50% relative to patients below this threshold. Conclusion FAP expression is significantly correlated with 68GaGa-FAPI-04 uptake and pre-treatment 68GaGa-FAPI-04 PET/CT parameters can predict survival outcomes for STS patients. Advances in knowledge Clinical utility of 68GaGa-FAPI-04 in STS remains unclear, and there aren’t many similar studies in the literature. We evaluated the role of 68GaGa-FAPI-04 in the prognosis of STS.