Evaluating the diagnostic value of 18F-FAPI-04 PET/CT in various malignant tumors: a head-to-head comparison with 18F-FDG PET/CT

Purpose This study aims to evaluate the diagnostic efficacy of F-18-fibroblast activation protein inhibitor-04 (F-18-FAPI-04) PET/CT for various malignant tumors and compare it head-to-head with F-18-FDG PET/CT. Materials and methods This single-center, prospective study continuously recruited patients with suspected or confirmed malignant tumors for concurrent 18F-FDG and 18F-FAPI-04 PET/CT scans from April 2022 to October 2023. The pathological diagnosis or clinical follow-up served as the reference standard. The Z-test for two proportions was used to compare the sensitivity, specificity, and accuracy of tumor diagnosis between the two imaging agents. Wilcoxon signed-rank tests were employed to compare the uptake of the two radiotracers and the tumor-to-background ratio (TBR) differences in tumors. Results The study involved 15 types of tumors and included 88 patients, comprising 53 males and 39 females, with an average age of 57.7 +/- 10.8 years. In patient-based analysis, 18F-FAPI-04 PET/CT demonstrated higher diagnostic accuracy than 18F-FDG PET/CT for both initial staging and restaging patients (77.4% vs 56.6%, p = 0.0389; 94.3% vs 54.3%, p < 0.001), prompting treatment plan adjustments in 17% of restaged patients. The lesion-based analysis revealed comparable diagnostic accuracy of 18F-FAPI-04 PET/CT and 18F-FDG PET/CT for primary tumors (78.9% vs 75.4%, p = 0.8234), while showing superior accuracy for residual/recurrent tumors, lymph node metastases, and distant metastases compared to 18F-FDG PET/CT (100.0% vs 50.0%, p = 0.002; 98.8% vs 86.0%, p < 0.001; 98.3% vs 79.3%, p < 0.001). Conclusion 18F-FAPI-04 PET/CT exhibits higher uptake and TBR in most tumors demonstrating superior diagnostic efficacy for primary lesions, residual/recurrent disease, and metastases compared to 18F-FDG PET/CT, particularly beneficial for restaging post-treatment patients.