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

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).

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.

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.

[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.