Biological-guided Metronomic Chemotherapy as Maintenance Strategy in Metastatic Colorectal Cancer

Based upon biological behavior, those mCRC patients who respond well (SD, PR or CR according to RECIST Criteria) after 16-18 weeks of standard doublet chemotherapy as induction may enrolled into this study, randomly divided into capecitabine metronomic group or standard dosage group. The duration of disease control after randomization(PFS2) and progression free survival from enrollment (PFS1) are primary endpoints. Meanwhile, the overall survival, safety and quality of life are secondary endpoints. Exploratory markers involving angiogenesis (serum VEGF, PDGF, Tie-1 and Tie2, etc) and immune function (CD clusters, serum tumor mutation burden(TMB), etc), are conducted via liquid biopsy.