Gallium-68-labeled fibroblast activation protein inhibitor PET in gastrointestinal cancer: insights into diagnosis and management

Purpose Gallium-68-labeled fibroblast activation protein inhibitor ( 68 Ga-FAPI) is an emerging promising tumor tracer. This study aims to evaluate the diagnostic efficiency of 68 Ga-FAPI PET in gastrointestinal cancer, and to determine its potential impact on clinical management. Methods Patients with malignancies were prospectively enrolled in a clinical trial to evaluate the diagnostic value of 68 Ga-FAPI PET. One hundred twenty patients with gastrointestinal malignancies (121 68 Ga-FAPI PET scans) between June 2020 and May 2021 were retrospectively analyzed. Initial staging of untreated patients and restaging of treated patients were evaluated. The treatment scheme promoted by imaging was determined according to NCCN guidelines. Final diagnosis and treatment reference standards were determined by a dedicated multidisciplinary team. The diagnostic performance and treatment guidance of 68 Ga-FAPI PET were compared with those of conventional imaging (CI) and 18 F-FDG PET. Results The diagnostic accuracy of 68 Ga-FAPI PET was much higher than that of CI and 18 F-FDG PET (95.0% vs. 65.1% and 69.0%, respectively, both p < 0.001). 68 Ga-FAPI PET revised diagnosis in 30.3% and 26.2% of patients compared with CI and 18 F-FDG PET. The accordance rate of 68 Ga-FAPI PET-guided treatment in comparison with the reference standard was significantly higher than that of CI and 18 F-FDG PET (96.7% vs. 75.2% and 76.2%, respectively, both p < 0.001). 68 Ga-FAPI PET changed treatment in 22.9% and 23.8% of patients compared with CI and 18 F-FDG PET. Conclusions 68 Ga-FAPI PET showed remarkable diagnostic performance in gastrointestinal cancer, resulting in more accurate staging and guidance for timely treatment revision, thereby having a critical impact on clinical management. Trial registration NCT04554719. Registered September 8, 2020—retrospectively registered, http://clinicaltrails.gov/show/NCT04554719