[68Ga]Ga-DOTA-FAPI-04 PET/CT in The Staging of Gastric Cancer: Improved Diagnostic Efficacy Confirmed By Postoperative Histopathology

Purpose: This study aimed to compare the diagnostic performance of [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F]-FDG PET/CT in the primary and metastatic lesions of gastric cancer. Methods Fifty-six patients with histologically proven gastric carcinomas were enrolled in this study. Each patient underwent both [ 18 F]-FDG and [ 68 Ga]Ga-FAPI-04 PET/CT within one week. Activity of tracer accumulation in lesions were assessed by maximum standardized uptake value (SUV max ) and TBR (lesions SUV max / ascending aorta SUV mean ). Histological work-up including immunohistochemical staining for FAP served as a standard of reference. Results [ 68 Ga]Ga-FAPI PET/CT is superior in detecting primary tumors both in patient-based (100% [45/45] vs. 97.8% [44/45]) and lesion-based analyses (97.8% [45/46] vs. 95.7% [44/46]), showing higher SUV max (10.25 vs. 8.13, P = 0.004) and TBR (11.63 vs. 5.83, P < 0.001), compared with [ 18 F]-FDG PET/CT. The specificity and positive predictive value of [ 68 Ga]Ga-FAPI were significantly higher than that of [ 18 F]-FDG (100.0% vs. 97.7%, P < 0.001; 100.0% vs. 57.1%, P = 0.001) in determining the lymph node (LN) metastases. [ 68 Ga]Ga-FAPI PET/CT was superior to [ 18 F]-FDG PET/CT in N-staging (47.1% [8/17] vs. 23.5% [4/17]), and in evaluation for LN, peritoneum and bone metastases. [ 68 Ga]Ga-FAPI PET/CT detected positive recurrent lesions in all patients and showed more positive lesions and clearer tumor delineation. Two patients underwent follow-up [ 68 Ga]Ga-FAPI PET/CT scans after chemotherapy, which both showed remission. Conclusions [ 68 Ga]Ga-FAPI PET/CT can better detect primary gastric cancer and metastatic lesions in peritoneum, abdominal LNs and bone, showing high usefulness in guiding N staging. Furthermore, [ 68 Ga]Ga-FAPI PET/CT provides more information for patients with recurrence detection and also has great potential in monitoring response to treatment.