Personalized PET Imaging in Gastric Cancer: An Umbrella Review of Meta‐Analyses to Guide Radiopharmaceutical Selection and Clinical Indication

Background Gastric cancer remains a leading cause of cancer‐related morbidity and mortality worldwide, and accurate imaging is critical for diagnosis, staging, recurrence detection, and prognostic assessment. Positron emission tomography (PET), traditionally performed using 18 F‐fluorodeoxyglucose (FDG), has demonstrated variable performance in gastric cancer, particularly for nodal and peritoneal disease. Recently, 68 Ga‐labeled fibroblast activation protein inhibitor (FAPI) PET has emerged as a promising alternative, prompting multiple systematic reviews and meta‐analyses with heterogeneous findings. Objective We are aimed at synthesizing and appraise meta‐analytic evidence on PET imaging in gastric cancer, with a focus on radiopharmaceutical‐specific performance by clinical indication and certainty of evidence to inform personalized tracer selection. Methods An umbrella review was conducted in accordance with PRISMA 2020. The protocol was prospectively registered in the Open Science Framework (OSF). PubMed, Scopus, and Web of Science were searched from inception to December 2025 for systematic reviews and meta‐analyses evaluating PET imaging in gastric cancer. Outcomes included diagnostic accuracy, staging and restaging performance, recurrence detection, prognostic associations, methodological quality (AMSTAR‐2), and certainty of evidence (GRADE). Results Eleven meta‐analyses published between 2011 and 2025 were included. FDG PET/CT demonstrated moderate diagnostic performance overall, with high specificity but limited sensitivity for lymph node and peritoneal metastases, while retaining moderate certainty for prognostic assessment based on standardized uptake value (SUV)–derived metrics. In contrast, 68 Ga‐FAPI PET generally showed higher pooled sensitivity than FDG for primary tumor detection, nodal disease, peritoneal metastases, and recurrence detection across available meta‐analyses, although the certainty of evidence ranged from low to moderate and some findings were derived from mixed‐population reviews. Conclusions Available meta‐analytic evidence suggests an indication‐driven, personalized approach to PET imaging in gastric cancer. FDG PET remains useful for prognostic stratification and selected recurrence settings, whereas FAPI PET appears to offer higher diagnostic sensitivity for staging and restaging, particularly for peritoneal disease. Nevertheless, the overall certainty of evidence remains limited by heterogeneity, indirectness, and the absence of updated de novo pooled analyses.