Head-to-head evaluation of [(18)F]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 [(18)F]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 [(18)F]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 (SUV(max) and TBR) of [(18)F]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 [(18)F]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 SUV(max) and TBR than [(18)F]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 SUV(max) and TBR presented favorable uptake of [(18)F]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 [(18)F]FDG for identifying recurrent lesions of liposarcoma, MSFT, and IDCS. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00259-022-05700-4.