Evaluation of FAPI PET imaging in gastric cancer: a systematic review and meta-analysis

Purpose: Recent studies suggest that 68 Ga-FAPI PET/CT demonstrated superiority over 18 F-FDG PET/CT in the evaluation of various cancer types, especially in gastric cancer (GC).By comprehensively reviewing and analysing the differences between 68 Ga-FAPI and 18 F-FDG in GC, some evidence is provided to foster the broader clinical application of FAPI PET imaging.Methods: In this review, studies published up to July 3, 2023, that employed radionuclide labelled FAPI as a diagnostic radiotracer for PET in GC were analysed.These studies were sourced from both the PubMed and Web of Science databases.Our statistical analysis involved a bivariate meta-analysis of the diagnostic data and a meta-analysis of the quantitative metrics.These were performed using R language.Results: The meta-analysis included 14 studies, with 527 patients, of which 358 were diagnosed with GC.Overall, 68 Ga-FAPI showed higher pooled sensitivity (0.84 [95% CI 0.67-0.94]vs. 0.46 [95% CI 0.32-0.60]),specificity (0.91 [95% CI 0.76-0.98]vs. 0.88 [95% CI 0.74-0.96])and area under the curve (AUC) (0.92 [95% CI 0.77-0.98]vs. 0.52 [95% CI 0.38-0.86])than 18 F-FDG.The evidence showed superior pooled sensitivities of 68 Ga-FAPI PET over 18 F-FDG for primary tumours, local recurrence, lymph node metastases, distant metastases, and peritoneal metastases.Furthermore, 68 Ga-FAPI PET provided higher maximum standardized uptake value (SUVmax) and tumour-to-background ratios (TBR).For bone metastases, while 68 Ga-FAPI PET demonstrated slightly lower patient-based pooled sensitivity (0.93 vs. 1.00), it significantly outperformed 18 F-FDG in the lesion-based analysis (0.95 vs. 0.65).However, SUVmax (mean difference ) and TBR .80]) of bone metastases showed no significant difference between 68 Ga-FAPI PET/CT and 18 F-FDG PET/CT.Conclusion: Compared with 18 F-FDG, 68 Ga-FAPI PET imaging showed improved diagnostic accuracy in the evaluation of GC.It can be effectively applied to the early diagnosis, initial staging, and detection of recurrence/metastases of GC. 68 Ga-FAPI may have the potential of replacing 18 F-FDG in GC in future applications.