Study of Bevacizumab Plus Chemotherapy in Patients With Metastatic Colorectal Cancer

This study evaluates the relationship of biomarker expression and efficacy of bevacizumab plus chemotherapy in patients with unresectable/metastatic colorectal cancer. Before the treatment, the investigators detect the VEGF-A,VEGF-C,VEGF-D,VEGFR-1,VEGFR-2,VEGFR-3 expression in tumor tissue by IHC and detect those protein expression level in plasma by ELISA. After at least 6 weeks treatment, the investigators detect again VEGF-A,VEGF-C,VEGF-D expression level in plasma by ELISA. The aim of the study is to identify whether those biomarkers could predict Bevacizumab efficacy.