Serum tumor antigen REG4 as a useful diagnostic biomarker in gastric cancer

Background/Aim: Serum biomarkers for the detection of gastric cancer are needed even now in order to find a larger number of candidates for suspected gastric cancer. We evaluated the usefulness of a novel serum marker, REG4, as compared to that of CA19-9, CEA, and pepsinogen. Methodology: Pre-therapeutic sera were collected from 74 patients with gastric cancer and 106 healthy controls without any cancers. REG4, CEA, CA19-9, and pepsinogen serum levels were measured in each group. The cut-off value of REG4 was defined, and then the usefulness of REG4 was evaluated with a validation study that included sera collected from 37 patients with gastric cancer and 44 healthy controls without any cancers. Results: REG4 levels were significantly higher in early gastric cancer patients (median 8.42 ng/ml) than in controls (median 5.01 ng/ml) (p<0.001), and in advanced gastric cancer patients (median 13.12 ng/ml) than in early gastric cancer patients (p<0.02). A cut-off value of 6.67 ng/ml was defined using the receiver operating characteristics curve. The sensitivity for gastric cancer was 73.0%, the specificity was 70.8%, and the accuracy was 71.8%. Diagnostic accuracy of REG4 was superior to that of the other tests. In the validation study, the sensitivity for gastric cancer was 94.5%, the specificity was 31.8%, and the accuracy was 60.5%. Conclusions: Serum REG4 level can be a useful indicator to distinguish between patients with gastric cancer and healthy subjects. This has the potential to be used as a screening serum marker for gastric cancers, including cancers in the early stages.