Superiority of [68Ga]Ga-FAPI-04 Over [18F]-FDG PET/CT and Conventional Imaging in Detecting Peritoneal Carcinomatosis.

BACKGROUND

This study aimed to investigate the diagnostic value of [gallium-68]-labeled fibroblast activation protein inhibitor ([68Ga]Ga-FAPI-04) versus [fluorine-18]-fluorodeoxyglucose positron emission tomography/computed tomography ([18F]-FDG PET/CT), contrast-enhanced computed tomography (CECT), and magnetic resonance imaging (MRI) in detecting peritoneal carcinomatosis (PC).

METHODS

The study enrolled patients with suspected peritoneal malignancy. [68Ga]Ga-FAPI-04 PET/CT was compared with three alternative modalities in terms of diagnostic efficacy and quantitative metrics. Diagnostic performance was assessed across morphologic subtypes in confirmed PC.

RESULTS

In this study, 261 patients underwent [68Ga]Ga-FAPI-04 and [18F]-FDG PET/CT, 155 completed CECT, and 43 completed MRI. Patient-based detection accuracy for PC improved from 65.2 % (101/155) for CECT, 83.7 % (36/43) for MRI, and 87.7 % (229/261) for [18F]-FDG PET/CT to 95.8 % (250/261) for [68Ga]Ga-FAPI-04 PET/CT. The region-based diagnostic accuracy improved from 47.8 % (97/203) for CECT, 73.1 % (49/67) for MRI, and 61.1 % (124/203) for [18F]-FDG PET/CT to 92.6 % (188/203) for [68Ga]Ga-FAPI-04 PET/CT. Compared with [18F]-FDG PET/CT, CECT and MRI, [68Ga]Ga-FAPI-04 PET/CT detected more involved peritoneal metastatic regions and thus produced a higher peritoneal cancer index (PCI) score (median PCI, 8 vs 5 vs 2 vs 4). For semiquantitative evaluation, [68Ga]Ga-FAPI-04 PET/CT exhibited a significantly higher maximum standardized uptake value (SUVmax) (5.1 ± 2.6 vs 4.2 ± 3.0), SUVmean (3.1 ± 1.4 vs 2.5 ± 1.4), and tumor-to-background ratio (TBR) (7.8 ± 4.8 vs 2.6 ± 1.9) for PC than [18F]-FDG (P < 0.001). Across all five morphologic subtypes of PC, [68Ga]Ga-FAPI-04 PET/CT maintained superior diagnostic performance over both [18F]-FDG PET/CT and CECT.

CONCLUSIONS

[68Ga]Ga-FAPI-04 PET/CT outperformed CECT, MRI, and [18F]-FDG PET/CT for PC detection, with consistent performance across all morphologic subtypes. Its superiority may improve clinical decision-making, rendering it the preferred modality for inconclusive alternative imaging.