Clinical Application of Capecitabine in Maintenance Chemotherapy for Advanced Colorectal Cancer: a Randomized Control Trial

INTERVENTION: Group A:Capecitabine 1g/m2 bid d1‐14 q3w;Group B:Observation; CONDITION: Recurrent/ Metastatic colorectal cancer PRIMARY OUTCOME: Time to progression; SECONDARY OUTCOME: Overall survival;Adverse reaction; INCLUSION CRITERIA: 1. Male and female patients aged more than 18 years old; 2. KPS score >=70; 3. Advanced colorectal cancer confirmed by histology or cytology, or irremovable advanced colorectal adenocarcinoma; 4. Patients have received the first‐line chemotherapy such as FOLFOX (Oxaliplatin + 5‐FU/CF) or XELOX (Capecitabine+ Oxaliplatin) or FOLFIRI (Irinotecan+ 5‐FU/CF) or XERILI (Capecitabine+ Oxaliplatin) for 16‐24 weeks and reach the complete response, partial response or stable disease according to Response Evaluation Criteria in Solid Tumors; 5. Patients must be enrolled at least 4 weeks after the last radiotherapy and the measurable lesion is not in the radiation scope; 6. Absolute count of Neutrophils >1.5*10^9/L, Platelets count >100*10^9/L, total serum bilirubin <1* upper limit of normal range. AST and ALT<2*upper limit of normal range (if the liver dysfunction was caused by the tumor, it should be less than 5*upper limit of normal range; 7. Expected