Comparison of [68Ga]Ga-FAPI and [18F]FDG uptake in patients with gastric signet-ring-cell carcinoma: a multicenter retrospective study

Eur Radiol. 2023 Feb;33(2):1329-1341. doi: 10.1007/s00330-022-09084-9. Epub 2022 Aug 17.


Objective: In this study, we investigated the role of [68Ga]Ga-FAPI PET imaging in the detection of primary and metastatic gastric signet-ring-cell carcinoma (GSRCC) and compared with [18F]FDG PET.

Methods: This retrospective multicenter analysis included 34 patients with histologically confirmed GSRCCs from four medical centers. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), and diagnostic accuracy were compared between the two modalities. [18F]FDG and [68Ga]Ga-FAPI uptakes were compared by using the Wilcoxon signed-rank test. McNemar's test was used to compare the diagnostic accuracy between the two techniques.

Results: Data were analyzed from 27 paired PET/CT and 7 paired PET/MRI scans for 34 GSRCC patients (16 men and 18 women) who had a median age of 51 years (range: 25-85 years). [68Ga]Ga-FAPI PET showed higher SUVmax and TBR values than did [18F]FDG PET in the primary tumors (SUVmax: 5.2 vs. 2.2, p = 0.001; TBR: 7.6 vs. 1.3, p < 0.001), involved lymph nodes (SUVmax: 6.8 vs. 2.5, p < 0.001; TBR: 5.8 vs. 1.3, p < 0.001), and bone and visceral metastases (SUVmax: 6.5 vs. 2.4, p < 0.001; TBR: 6.3 vs. 1.3, p < 0.001). In diagnostic performance, [68Ga]Ga-FAPI PET exhibited higher sensitivity than [18F]FDG PET for detecting primary tumors (73% [16/22] vs. 18% [4/22], p < 0.001), local recurrences (100% [7/7] vs. 29% [2/7], p = 0.071), lymph node metastases (77% [59/77] vs. 23% [18/77], p < 0.001), and distant metastases (93% [207/222] vs. 39% [86/222], p < 0.001).

Conclusion: The results from this multicenter retrospective analysis justify the clinical use of [68Ga]Ga-FAPI tracers for GSRCC diagnosis and staging.

Key points: • [68Ga]Ga-FAPI PET/CT is a promising imaging modality for the detection of primary and metastatic disease and has implications for TNM staging in GSRCC. • In this multicenter study of 34 patients with GSRCC, [68Ga]Ga-FAPI PET exhibited greater radiotracer uptake, tumor-to-background ratios, and diagnostic accuracy than [18F]FDG PET for detecting primary/recurrent tumors and metastatic lesions.

Keywords: Gastric cancer; PET/CT; PET/MRI; [18F]FDG; [68Ga]Ga-FAPI.

Publication types

  • Multicenter Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Carcinoma*
  • Female
  • Fluorodeoxyglucose F18
  • Gallium Radioisotopes
  • Humans
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local
  • Neoplasms, Second Primary*
  • Positron Emission Tomography Computed Tomography
  • Retrospective Studies
  • Stomach Neoplasms* / diagnostic imaging


  • Fluorodeoxyglucose F18
  • Gallium Radioisotopes