The Impact of Baseline 18F-FDG PET-CT on the Management and Outcome of Patients with Gastric Cancer: a Systematic Review

Objective: CT and staging laparoscopy are routinely used to stage patients with gastric cancer, however the role of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) combined with CT (PET-CT) is uncertain. This systematic review synthesised the evidence regarding the impact of baseline PET-CT staging on treatment decisions and patient outcomes. Methods: Systematic database searches were performed without date restriction. Studies reporting data in patients with gastric adenocarcinoma who underwent radiological staging were included. One reviewer screened titles and abstracts for suitability and two reviewers extracted data from included articles. Primary outcome was the reported change in management after PET-CT. Secondary outcomes were the rates of recurrence and overall survival between patients staged with and without PET-CT. Risk of bias was assessed using the ROBINS-I tool. PROSPERO registration (CRD42022304314). Results: Data from 11 studies recruiting 2101 patients between 2012 and 2021 were included. PET-CT was performed in 1422 patients. Change of management varied between 3% and 29% of cases. No studies compared recurrence or survival rates between patients staged with or without PET-CT. Adenocarcinoma of intestinal subtype tended to be more FDG-avid compared to diffuse or signet-ring subtypes. No randomised data existed, and studies were considered low quality with high risk of bias. Conclusion: Evidence for the additional value of PET-CT in the gastric cancer staging pathway is limited. All studies reported a positive impact by preventing those with undetected metastatic disease on CT undergoing futile surgery. Future national guidelines should consider routine staging PET-CT in gastric cancer. Advances in knowledge: Studies indicated that FDG PET-CT added benefit in gastric cancer staging by detecting more distant metastases, but these studies were generally of low quality and at high risk of bias. Intestinal subtype of gastric adenocarcinoma tended to be more FDG-avid and therefore more distant metastases were subsequently detected.