Further analysis of serum CFD levels and clinical TNM staging showed that the serum CFD concentration in early (stage I) GC patients was significantly higher than that in healthy controls, but except CA72-4 there was no significant elevation in serum CEA, CA19-9 and CA50 levels, suggesting that the elevation of serum CFD is an early event in GC carcinogenesis compared with the traditional tumor biomarkers, and serum CFD detection may be of great significance in early GC screening and diagnosis. This evidence concerns the gene CEACAM5 and gastric cancer.