The serum CFD concentration in initial (stage I) GC individuals was substantially higher than that in healthy participants, according to an additional analysis of serum CFD levels and clinical TNM staging, but there was no substantial rise in serum CEA, CA19-9, or CA50 levels, indicating that the elevation of serum CFD is an earlier event in GC carcinogenesis than the classical tumor biomarkers, and serum CFD detection may be of major relevance in early GC. Here, CEACAM5 is linked to gastric cancer.