Superiority of 18F-FAPI-42 PET/CT in the detection of primary tumor and management of appendiceal neoplasm to 18F-FDG PET/CT and CE-CT.

Background: In the present study, we investigated the value of ¹⁸F-fibroblast-activation protein inhibitor (FAPI) positron emission tomography/computed tomography (¹⁸F-FAPI-42 PET/CT) to preoperative evaluations of appendiceal neoplasms and management for patients.

Methods: This single-center retrospective clinical study, including 16 untreated and 6 treated patients, was performed from January 2022 to May 2023 at Southern Medical University Nanfang Hospital. Histopathologic examination and imaging follow-up served as the reference standard. ¹⁸F-FAPI-42 PET/CT was compared to ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT and contrast-enhanced CT (CE-CT) in terms of maximal standardized uptake value (SUVmax), diagnostic efficacy and impact on treatment decisions.

Results: The accurate detection of primary tumors and peritoneal metastases were improved from 28.6% (4/14) and 50% (8/16) for CE-CT, and 43.8% (7/16) and 85.0% (17/20) for ¹⁸F-FDG PET/CT, to 87.5% (14/16) and 100% (20/20) for ¹⁸F-FAPI-42 PET/CT. Compared to ¹⁸F-FDG PET/CT, ¹⁸F-FAPI-42 PET/CT detected more regions infiltrated by peritoneal metastases (108 vs. 43), thus produced a higher peritoneal cancer index (PCI) score (median PCI: 12 vs. 5, P < 0.01). ¹⁸F-FAPI-42 PET/CT changed the intended treatment plans in 35.7% (5/14) of patients compared to CE-CT and 25% (4/16) of patients compared to ¹⁸F-FDG PET/CT but did not improve the management of patients with recurrent tumors.

Conclusions: The present study revealed that ¹⁸F-FAPI-42 PET/CT can supplement CE-CT and ¹⁸F-FDG PET/CT to provide a more accurate detection of appendiceal neoplasms and improved treatment decision making for patients.