To investigate the effect of Tislelizumab combined with XELOX in Neoadjuvant Therapy for gastrointestinal tumors.~To explore new biomarkers that can predict the efficacy of combined immunotherapy, and to establish a clinical efficacy prediction model by means of bioinformatics to prospectively judge the efficacy and guide the follow-up individualized and accurate treatment.
immunotherapy，gastric cancer，rectal cancer，biomark