CEACAM5 and cancer: Noninvasive serological markers, including carcinoembryonic antigen, cancer antigen 19-9 (CA19-9), CA724, CA125, and α-fetoprotein, are inadequate for GC detection owing to low specificity and sensitivity, especially for early-stage cancers.6 Thus, there is an unmet clinical need for cost-effective, minimally invasive approaches for early GC detection.