ERBB2 and mismatch repair cancer syndrome 1: The most common predictive biomarkers currently used in GEAs are microsatellite instability or mismatch repair deficiency status and expression of human epidermal growth factor receptor 2 (HER2) and programmed death-ligand 1 (PD-L1).16,17 There are other biomarkers that will soon have therapeutic implications, such as Claudin 18.2 and FGFR2b.18,19 The use of these predictive biomarkers has helped us tailor treatments for patients with GEA, yet there is still an unmet need to identify additional targets for novel treatment strategies.