Combined Positron Emission Tomography and Computed Tomography Using 68Ga-FAPI in the Diagnosis of Gastric Cancer Metastases and Evaluation of Antitumor Treatment Effectiveness

Gastric cancer (GC) remains one of the leading causes of cancer-related morbidity and mortality worldwide, ranking fifth in morbidity and fourth in mortality, with 1,089,103 new cases and 768,793 deaths recorded globally in 2022. This corresponds to a high mortality-to-incidence ratio of approximately 0.70, underscoring its aggressive clinical behavior and late-stage presentation. In Kazakhstan, the burden of GC is particularly significant: it ranks among the five most prevalent malignancies in the country, accounting for 11.43% of all oncological deaths and emphasizing its major contribution to national cancer mortality. Positron emission tomography/computed tomography (PET/CT) has become a cornerstone in oncologic imaging due to its dual ability to assess both metabolic activity and anatomical details. However, 18 F-fluorodeoxyglucose ( 18 F-FDG), the most commonly used radiotracer, has well-recognized limitations in GC. Low 18 F-FDG uptake is noted in mucinous, signet-ring cell, poorly differentiated tumors, and inflammation. These factors reduce its sensitivity and diagnostic accuracy. In contrast, fibroblast activation protein inhibitor 68 Ga-FAPI enables superior tumor-to-background contrast and improve visualization of lesions with low glucose metabolism. Rapid blood clearance and high FAP expression in GC further enhance detection of lymphatic, peritoneal, and distant metastases. The aim of this literature review was to provide a comprehensive evaluation of 68 Ga-FAPI PET/CT in early diagnosis, staging, and treatment monitoring of GC, as well as analyse its efficacy compared to standar d 18 F-FDG PET/CT.