Development of a liquid-biopsy-based technique for the supplementary diagnosis of highly advanced lymph node metastasis in patients with locally advanced gastric cancer.

56 Background: The outcomes of patients with locally advanced gastric cancer who have highly advanced lymph node metastasis such as N3 remain poor despite radical resection. If the preoperative diagnoses of such patients improve, further improvement in treatment outcomes is expected to be obtained by means of personalized therapies such as preoperative chemotherapy; however, the accuracy of diagnosis remains unsatisfactory. Therefore, exploratory proteome analysis using sera was performed with the aim of developing a supplementary liquid-biopsy-based technique to diagnose highly advanced lymph node metastasis in patients with locally advanced gastric cancer. We report the results obtained thus far. Methods: The subjects were 24 patients with pT4a gastric cancer (12 with pN0 disease and 12 with pN3 disease). Proteins that had significantly different (P<0.001) expression levels in the preoperative serum on exploratory proteome analysis by liquid chromatography and mass spectrometry were identified. These proteins were verified by Enzyme-Linked ImmunoSorbent Assay (ELISA) using a different cohort (20 patients with pN0 disease and 13 with pN3 disease) from that described above. Results: In the exploratory proteome analysis, 2,357 kinds of proteins were identified and examined. Six these proteins were identified as candidate predictive markers of highly advanced lymph node metastasis. These proteins were verified using existing and newly developed ELISA kits, and reproducibility was verified for one protein (Protein V) (P = 0.003). Conclusions: The possibility of the supplementary diagnosis of highly advanced lymph node metastasis by liquid biopsy was suggested in patients with locally advanced gastric cancer. Further evaluations by prospective studies are now in progress, with the ultimate goal of clinical application.