Clinical Significance of Circulating Tumor Cells (CTCs) in Blood of Patients With Advanced/Metastatic Gastric Cancer

"Collect peripheral blood sample of 100 gastric cancer patients pre-chemotherapy treated with capecitabine/paclitaxel (XPa) and capecitabine/cisplatin (XP) and post two cycles of chemotherapy(response evaluation).~Blood samples will be transferred to central lab to detect CTCs by Cellsearch kit.~Tumor response evaluation will be performed after two cycles of chemotherapy by CT/MRI based on RECIST. Clinical data, including tumor stage, metastastic organ, chemotherapy regimen, objective response, progression free survival, overall survival, etc, will be collected according to study protocol."