Gastric cancer(GC) is one of the common malignant tumors in world, with relatively high incident rate and mortality among the population. Neoadjuvant chemotherapy is often needed before operation for locally advanced or resectable gastric or gastro-oesophageal junction cancer. Neoadjuvant chemotherapy should be combined with platinum and fluorouracil, or paclitaxel should be added on the basis of platinum and fluorouracil. The efficacy of neoadjuvant chemotherapy for GC patients is usually evaluated by computer tomography(CT) scans with RECIST 1.1 criteria and the blood level of carcinoembryonic antigen(CEA),CA19-9 (carbohydrate antigen 19-9)and CA72-4(carbohydrate antigen 72-4) tumor markers.~CTC originating from solid tumors are related to hematogenous metastatic spread to distant sites. Therefore, CTC analysis has clinical relevance as a biomarker to noninvasively monitor cancer progression and guide therapy.Moreover, ctDNA is a part of cfDNA derived from apoptotic, necrotic or secreted DNA fragments of tumor cells, ctDNA contains the same genetic defects as the tumor DNA of its origin, such as point mutation and rearrangement. We speculate CTC, ctDNA and cfDNA are new biomarkers for tumor, which can guide neoadjuvant chemotherapy and surgical treatment for patients with locally advanced or resectable gastric or gastro-oesophageal junction cancer.~In this study, investigators will compare the clinical value of the dynamic detection of CTC, ctDNA and cfDNA with CEA ,CA19-9 and CA72-4 tumor markers and CT scan according the RECIST 1.1 criteria in neoadjuvant chemotherapy and operation for resectable or locally advanced gastric or gastro-oesophageal junction cancer. Investigators will also explore the relationship between the dynamic changes of CTC, ctDNA and cfDNA and the prognosis of patients after operation. The results will provide lots of meaningful information which may further improve the treatment of locally advanced or resectable gastric or gastro-oesophageal junction cancer.
To explore the clinical value of dynamic detection of circulating tumor cells(CTCs), circulating tumor DNA(ctDNA) and cell-free DNA(cfDNA) in neoadjuvant chemotherapy and operation of resectable or locally advanced gastric or gastro-oesophageal junction cancer.