Comparison of Diagnostic Efficacy of [68Ga]Ga-FAPI-04 and [18F]FDG PET/CT for Staging and Restaging of Gastric Cancer

Abstract

Purpose: This study aimed to compare the potential diagnostic efficacy of gallium68-fibroblast-activation protein inhibitor ([⁶⁸Ga]Ga-FAPI-04) and fluorine18-fluorodeoxyglucose ([¹⁸F]-FDG) positron emission tomography-computed tomography (PET/CT) for primary tumors, lymph nodes, and distant metastatic lesions of gastric cancer (GC), and to explore the effects of [⁶⁸Ga]Ga-FAPI-04 and [¹⁸F]-FDG on tumor staging and restaging in GC.

Methods: This single-center retrospective study (NCT2100044131) was conducted at the Affiliated Hospital of the Southwest Medical University between June 2020 and December 2021. Images of patients with GC who were pathologically confirmed and underwent contemporaneous [¹⁸F]-FDG and [⁶⁸Ga]Ga-FAPI-04 PET/CT within 1 week were analyzed. The diagnostic efficacy of [⁶⁸Ga]Ga-FAPI-04 PET/CT and [¹⁸F]-FDG PET/CT for TNM staging of GC was compared using McNemar test. The maximum standard uptake value (SUVmax) of each lesion in the two imaging types was compared using the Mann-Whitney U test.

Results: In total, 25 patients with GC (mean age, 56 ± 12 years) were evaluated. [⁶⁸Ga]Ga-FAPI-04 PET/CT exhibited higher sensitivity compared to [¹⁸F]-FDG PET/CT for detecting primary tumors (18/19 [94.74%] vs. 13/19 [68.42%], χ2 = 6.866, P < 0.01), lymph node metastasis (75/77 [97.40%] vs. 32/77 [41.56%], χ2 = 2.888, P =0.089), and distant metastases (275/283 [97.17%] vs. 122/283 [43.11%], χ2 = 11.858, P < 0.01). [⁶⁸Ga]Ga-FAPI-04 accumulation was significantly higher than that of [¹⁸F]FDG in tumors (median SUVmax, 10.28 vs 3.20; U=59.00, P < 0.01), lymph node metastasis metastases (median SUVmax, 9.20 vs 3.15; U=53.50, P < 0.01), and distant metastases (median SUVmax, 8.00 vs 4.20; U=200.00, P < 0.01). Compared to [¹⁸F]-FDG PET/CT, [⁶⁸Ga]Ga-FAPI-04 PET/CT resulted in new oncological findings in 14/25 patients and corrected tumor staging or restaging in 7/25 patients.

Conclusion: Our preliminary results regarding the impact of [⁶⁸Ga]Ga-FAPI-04 PET/CT on tumor staging highlight the potential of this approach for increasing the accuracy of GC diagnosis, which may facilitate treatment decision-making.

Keywords: PET/CT; [18F]-FDG; [68Ga]Ga-FAPI-04; gastric cancer; tumor staging.

Figure 1

A 64-year-old woman with poorly differentiated gastric adenocarcinoma based on pathological biopsy under gastroscopy. Both [⁶⁸Ga]Ga-FAPI-04 (A, C) and [¹⁸F]-FDG PET/CT (F, H) were negative in the primary focus. Compared with [¹⁸F]-FDG PET/CT (E–G), [⁶⁸Ga]Ga-FAPI-04 PET/CT (B–D) resulted in a higher liver/background ratio and identified more liver lesions (slender arrows, SUVmax=6.3 vs. 11.3) and para-aortic lymph node metastases (dashed arrows, SUVmax=12.8 vs. 8.0).

Figure 2

A 47-year-old female patient with poorly differentiated gastric adenocarcinoma with partial signet ring cells based on pathological biopsy after operation. [⁶⁸Ga]Ga-FAPI-04 PET/CT (A–D) revealed high uptake in the gastric cardia (slender arrows, SUVmax=13.3), para-aortic lymph nodes (dashed arrows, SUVmax=15.7), and supraclavicular lymph nodes (short arrows, SUVmax=8.0) but negative uptake was observed on FDG PET/CT (E–H). [¹⁸F]-FDG PET/CT (F) revealed increased uptake in the gastric anastomosis (bent arrow, SUVmax=3.2) but negative uptake was observed on [⁶⁸Ga]Ga-FAPI-04 PET/CT (C). The lesion was ultimately confirmed as residual gastritis by gastroscopic biopsy.

Figure 3

A 35-year-old female patient with moderately differentiated gastric adenocarcinoma based on pathological biopsy under gastroscopy. [⁶⁸Ga]Ga-FAPI-04PET/CT (A–D) revealed high uptake in the primary tumor (arrows, SUVmax=8.3) but negative uptake was observed on [¹⁸F]-FDG PET/CT (E–H).

Figure 4

A 40-year-old female patient with poorly differentiated gastric adenocarcinoma based on pathological biopsy under gastroscopy. [⁶⁸Ga]Ga-FAPI-04 PET/CT (A–C) revealed high uptake in the primary tumor (slender arrows, SUVmax=10.3) and lesser curved lymph nodes in the stomach (triangles, SUVmax=3.2), but negative uptake was observed on [¹⁸F]-FDG PET/CT (E, F, H). [¹⁸F]-FDG PET/CT (H) revealed brown fat visualization at the base of the neck and in the supraclavicular fossa. [¹⁸F]-FDG PET/CT (G) revealed high uptake in the right ovarian (dashed arrows, SUVmax=8.2), but negative uptake was observed on [⁶⁸Ga]Ga-FAPI-04 PET/CT (D).

Figure 5

A 56-year-old male patient with poorly differentiated gastric adenocarcinoma based on pathological biopsy under gastroscopy. [⁶⁸Ga]Ga-FAPI-04 PET/CT (A–D) revealed high uptake in the primary tumor (slender arrows, SUVmax=14.6) and lesser curved lymph nodes of the stomach (dashed arrows, SUVmax=8.7), but moderate uptake in the primary tumor (bent arrows, SUVmax=5.3) and negative uptake of lesser curved lymph nodes of the stomach were observed on [¹⁸F]-FDG PET/CT (E–H).