Head-to-head evaluation of [18F]FDG and [68 Ga]Ga-DOTA-FAPI-04 PET/CT in recurrent soft tissue sarcoma.

PURPOSE: We aimed to evaluate the value of [68 Ga]Ga-DOTA-FAPI-04 PET/CT for the diagnosis of recurrent soft tissue sarcoma (STS), compared with [18F]FDG PET/CT. METHODS: A total of 45 patients (21 females and 24 males; median age, 46 years; range, 18-71 years) with 13 subtypes of STS underwent [18F]FDG and [68 Ga]Ga-DOTA-FAPI-04 PET/CT examination within 1 week for assessment local relapse or distant metastasis. Positive lesions on PET/CT images were verified by biopsy or 3-month follow-up. Wilcoxon matched-pairs signed-rank test was used to compare the semiquantitative values (SUVmax and TBR) of [18F]FDG and [68 Ga]Ga-DOTA-FAPI-04 in tumor lesions, and McNemar test was applied to test for differences of both tracers. RESULTS: Among the 45 patients, 282 local relapses and distant metastases were identified. Compared to [18F]FDG, [68 Ga]Ga-DOTA-FAPI-04 PET/CT detected more lesions (275 vs. 186) and outperformed in sensitivity, specificity, PPV, NPV, and accuracy for the diagnosis of recurrent lesions (P < 0.001). [68 Ga]Ga-DOTA-FAPI-04 demonstrated significantly higher values of SUVmax and TBR than [18F]FDG PET/CT in liposarcoma (P = 0.011 and P < 0.001, respectively), malignant solitary fibrous tumor (MSFT) (P < 0.001 and P < 0.001, respectively), and interdigitating dendritic cell sarcoma (IDCS) (P < 0.001and P < 0.001, respectively). While mean SUVmax and TBR presented favorable uptake of [18F]FDG over [68 Ga]Ga-DOTA-FAPI-04 in undifferentiated pleomorphic sarcoma (UPS) (P = 0.003 and P < 0.001, respectively) and rhabdomyosarcoma (RMS) (P < 0.001 and P < 0.001, respectively). CONCLUSION: [68 Ga]Ga-DOTA-FAPI-04 PET/CT is a promising new imaging modality for recurrent surveillance of STS, and compares favorably with [18F]FDG for identifying recurrent lesions of liposarcoma, MSFT, and IDCS.