In conclusion, the overall evidence in our study demonstrates that first-line immunotherapy for non-HER2-positive/HER2-negative advanced or metastatic GC or GEJC may not provide additional OS or PFS benefits in the negative-PD-L1-expressing (CPS < 1) or PD-L1-low subgroups (CPS 1–4/TAP < 5%) as compared with chemotherapy alone. This evidence concerns the gene CD274 and gastric cancer.