This study is try to evaluate the effect of capecitabine metronomic chemotherapy as maintenance treatment, which compare to capecitabine conventional chemotherapy, who have responded to 16-18 months first-line chemotherapy in metastatic colorectal cancer (mCRC). The maintenance treatments are continued until disease progression or severe toxicity. The aim of this study is to demonstrate that capecitabine metronomic chemotherapy is non-inferior to capecitabine conventional chemotherapy. Furthermore, 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.
