Comparative study of 18F-FAPI-04 and 18F-FDG PET/CT in the initial staging and postoperative metastasis detection of gastric cancer

Figure 1 Study population flowchart. FAPI: Fibroblast activation protein inhibitor; FDG: Fluorodeoxyglucose; PET/CT: Positron emission tomography/computed tomography.

Figure 2 A 76-year-old male underwent positron emission tomography/computed tomography to evaluate a gastric mass previously detected through Esophagogastroduodenoscopy. A: ¹⁸F-fibroblast activation protein inhibitor-04 positron emission tomography/computed tomography (PET/CT) images show one extremely strong uptake lesion (maximum standardized uptake value = 19.88) at the lesser curvature (solid line arrow), which were suspected of gastric cancer; B: ¹⁸F-fluorodeoxyglucose PET/CT images show mild tracer uptake (maximum standardized uptake value = 5.50) at the lesser curvature lesion (dotted line arrow). ¹⁸F-fibroblast activation protein inhibitor-04 PET/CT offered superior imaging contrast to ¹⁸F-fluorodeoxyglucose PET/CT, as evidenced by a significantly higher tumor-to-background ratio (19.88 vs 3.07) and better-defined tumor margins; C: The pathological findings derived from surgical resection are indicative of mucinous adenocarcinoma. HE: Hematoxylin-eosin; FAP: Fibroblast activation protein.

Figure 3 A 79-year-old male with gastric discomfort underwent both ¹⁸F-fibroblast activation protein inhibitor-04 and ¹⁸F-fluorodeoxyglucos positron emission tomography/computed tomography imaging for initial assessment. A: ¹⁸F-fibroblast activation protein inhibitor-04 positron emission tomography/computed tomography (PET/CT) images show mildly increased fluorodeoxyglucose (FDG) uptake (maximum standardized uptake value = 3.1) in the lymph nodes adjacent to the gastric antrum (solid line arrow); B: ¹⁸F-FDG PET/CT images also show mild tracer uptake (maximum standardized uptake value = 3.2) in the lymph nodes adjacent to the gastric antrum (dotted line arrow). Compared with ¹⁸F-FDG PET/CT, ¹⁸F-fibroblast activation protein inhibitor-04 PET/CT did not demonstrate a high tumor-to-background ratio (2.30 vs 2.39) and clearer tumor contour; C: The pathological findings derived from lymph node resection indicated the presence of metastatic disease. HE: Hematoxylin-eosin; FAP: Fibroblast activation protein.

Figure 4 A 64-year-old male with a history of gastric cancer surgery underwent positron emission tomography/computed tomography to monitor for recurrence and metastases. A: ¹⁸F-fibroblast activation protein inhibitor-04 positron emission tomography/computed tomography images displayed intensely diffuse uptake (maximum standardized uptake value = 11.8) in the peritoneal metastases (solid line arrow); B: ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography images displayed no uptake in peritoneal metastatic lesions (dotted line arrow). Additionally, fibroblast activation protein inhibitor demonstrated increased uptake in more lymph node and muscular lesions compared to fluorodeoxyglucose.

Figure 5 Compare the performance of ¹⁸F-fluorodeoxyglucose and ¹⁸F-fibroblast activation protein inhibitor-04 positron emission tomography in detecting primary tumors, lymph nodes, bone and peritoneal metastases, local recurrences. Data are presented descriptively without statistical hypothesis testing. No P values are shown. LNM: Lymph node metastases; Mets: Metastases; Recs: Recurrences; PET/CT: Positron emission tomography/computed tomography; ¹⁸F-FAPI: ¹⁸F-fibroblast activation protein inhibitor; ¹⁸F-FDG: ¹⁸F-fluorodeoxyglucose.