KDR and gastric cancer: Currently, the analysis of biomarkers of apatinib in the treatment of GC after chemotherapy is mainly based on serum VEGFR-2 (95), serum carbohydrate antigen 19-9, carcinoembryonic antigen (CEA), tumor supplied group factor (TSGF), tumor necrosis factor- α (TNF-α) and inflammatory factors (105, 107).