Fruquintinib Plus Capecitabine as Maintenance Treatment of RAS / BRAF Wild-type Metastatic Colorectal Cancer

Inclusion Criteria: * Patients with histologically confirmed metastatic colorectal adenocarcinoma; * 18-75 years old; * Eastern Cooperation Oncology Group (ECOG) performance score 0-1; * At least one evaluable lesion for disease assessment according to RECIST version 1.1; * Able to take oral medications; * Patient have achieved CR, PR or SD after up to 8 cycles of first-line standard FOLFOX / - FOLFIRI / XELOX / xeliri + cetuximab treatment, and remained unresectable; * If radiotherapy has been performed before enrollment, at least one lesion should be located outside the radiation field; * Adequate organ functions as assessed by the following laboratory requirements: Leukocytes≥3.0x10\^9/L, absolute neutrophil count≥1.5x10\^9/L, platelet count≥100x10\^9/L, hemoglobin≥9g/dL; serum bilirubin≤1.5x the upper limit of normal(ULN);Alanine aminotransferase(ALT) and aspartate aminotransferase(AST)≤2.5x ULN; serum creatinine≤1.5x ULN. * An expected survival of at least 12 weeks; * Fertile male or female patients volunteered to use effective contraceptive methods during the study period and within 6 months after the end of treatment; * Willing to provide written informed consent to study procedures. Exclusion Criteria: * Patients who have received fruquintinib; * Patients who have received TACE within 6 weeks before enrollment; * Participated in other unapproved or unlisted drug clinical trials in China within 4 weeks before enrollment, and received corresponding experimental drug treatment; * Patients with dysphagia, active peptic ulcer, intestinal obstruction, active gastrointestinal bleeding, peptic perforation, malabsorption syndrome or uncontrolled intestinal inflammatory diseases; * International normalized ratio (INR) \> 1.5 or partially activated prothrombin time (APTT) \> 1.5 × ULN； * The researchers judged clinically significant electrolyte abnormalities; * At present, the patient has hypertension that cannot be controlled by drugs, which is specified as: systolic blood pressure ≥ 140 mmHg and / or diastolic blood pressure ≥ 90 mmHg; * Patients currently have poorly controlled diabetes (fasting glucose level is greater than CTCAE grade 2 after regular treatment); * Have received any surgery or invasive treatment or operation within 4 weeks before enrollment (except venous catheterization, puncture and drainage, etc.); * Active or uncontrolled severe infection ≥ grade 2 according to National Cancer Institute Common Toxicity (NCI-CTC) criteria; * Uncontrolled central nervous system metastasis or previous brain metastasis; * Other malignant tumors in the past 5 years, except for skin basal cell or squamous cell carcinoma after radical surgery, or cervical carcinoma in situ; * Any kind of concurrent cardiac disease with clinical meanings, such as cardiovascular accident, myocardial infarction, thromboembolism or hemorrhage within 6 months before enrollment, congestive heart failure ≤New York Heart Association (NYHA) class 2; ventricular arrhythmias requiring drug treatment; LVEF \< 50%; * With positive urine protein and 24-hour urinary protein content\>1g; * Have a tendency of bleeding or clotting; * Known human immunodeficiency virus (HIV) infection; known history of clinically significant liver disease, including viral hepatitis; * The target lesions have received brachytherapy (radioactive particle implantation) within 60 days before admission; * Unrelieved toxic reactions higher than CTCAE V5.0 grade 1 caused by any previous anti-cancer treatment, excluding hair loss, lymphopenia and neurotoxicity ≤ grade 2 caused by oxaliplatin; * With any illness or medical conditions that may jeopardize the patient's compliance or interfere the analyses or judgements of study results; * Pregnancy or lactation at the time of study entry; * With fertility but refuse to contraception.