CEACAM5 and gastric cancer: CFD was detected in all stage I GC samples and its concentration was significantly higher than BGD group and healthy controls (P < 0.05) (Figure 3A), but for conventional tumor markers except CA72-4, there was no significant difference in CEA, CA19-9, and CA50 levels between stage I GC patients, BGD patients and healthy controls (Figure 3B–3E).