Abstract
The sensitivity of three biomarkers, carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9 and CA72-4, in combination has been identified to be greater than that of any of the biomarkers considered in isolation in cases of gastric cancer (GC). However, the fundamental cause underlying this phenomenon remains to be fully elucidated. In the present study, the differences and correlation of these three biomarkers were investigated in patients with GC in order to determine how the three biomarkers in combination work more effectively compared with any of the biomarkers considered alone. The serum levels of CEA, CA19-9 and CA72-4 of 216 patients with gastric adenocarcinoma were analyzed on admission to hospital. The differences in positive rates and the serum levels of CEA, CA19-9 and CA72-4 were analyzed using the χ(2) test and the non-parametric Wilcoxon two-sample test. Phi (f) correlation analysis was used to study the correlation among the expression (positive or not) levels of CEA, CA19-9 and CA72-4. The correlation among the serum levels of biomarkers was analyzed using Spearman's test. The results demonstrated that the combined positive rate of CEA, CA19-9 and CA72-4 was significantly higher compared with the individual CEA, CA19-9 and CA72-4 positive rates (44.91% vs. 22.69, 18.98 and 22.69%, respectively; all P<0.05). The positive rate of CA19-9 and CA72-4 in the extent of the primary tumor/involvement of regional lymph node/distant metastases (TNM)-III/IV stage subgroup was higher compared with that in the TNM-I/II subgroup (χ(2)=5.902, P=0.015; χ(2)=8.009, P=0.005), although not the positive rate of CEA (χ(2)=0.302, P=0.583). A significant correlation was identified between the expression level of CEA and CA72-4 (f correlation coefficient=0.182; P=0.008) and between that of CA19-9 and CA72-4 (f correlation coefficient=0.189; P=0.006), although not between that of CEA and CA19-9 (f correlation coefficient=0.048; P=0.482) in the total number of patients with GC. A significant correlation was also identified between the serum levels of CEA and CA19-9, of CEA and CA72-4 and of CA19-9 and CA72-4 (Spearman's correlation coefficient=0.231, -0.271 and 0.167; P=0.001, P<0.0001 and P=0.014, respectively). The present study indicated that there was only a weak correlation between the positive rate of CEA and CA72-4 and between that of CA19-9 and CA72-4, and no correlation was identified between the positive rate of CEA and CA19-9, even if a correlation was identified between the serum levels of the biomarkers. The present study suggested that the evidence that the sensitivity of the three biomarkers in combination is greater than that of any of the biomarkers taken in isolation is due to less co-presentation of CEA, CA19-9 and CA72-4 in patients with GC.