Using an optimal diagnostic cut off value of 425 EU, individual IgA had the highest sensitivity (52.1%) for discrimination of ESCC from non-ESCC controls compared with conventional serum markers for ESCC, such as SCCA, CYFRA21-1, CEA, CA19-9 [37–41], whereas the specificity was low (70.8%). This evidence concerns the gene CEACAM5 and esophageal squamous cell carcinoma.