Clinical Study of Apatinib Combined With Second - Line Chemotherapy for Metastatic Colorectal Cancer

Inclusion Criteria: 1. Male or female aged 18 to 70 years old; 2. Histologically or cytologically proven patients with metastatic colorectal cancer have undergone a first-line standard regimen recommended by the NCCN guidelines for progression; 3. According to the RECIST 1.1 criteria, the patient has at least one target lesion that can measure the diameter; 4. ECOG PS ≤ 2; 5. Expected survival time of more than 12 weeks. 6. The level of organ function must meet the following requirements: Bone marrow: neutrophil count (ANC) ≥ 1.5 × 10\^9/L, platelet ≥ 75 × 10\^9/L, hemoglobin ≥ 90g/L. Liver: serum bilirubin ≤ 2 times the upper limit of normal, aminotransferase AST and ALT ≤ 2.5 times the normal upper limit. Kidney: Serum creatinine ≤1.5 times upper limit of normal. 7. Patient compliance is good; 8. Understand and voluntarily sign a written informed consent. Exclusion Criteria: 1. Other previous or concurrent malignancy, except cured skin basal cell carcinoma and cervical carcinoma in situ; 2. Already known to be allergic to apatinib or any excipient; 3. Use unapproved drugs or other test medications within 4 weeks prior to enrollment; 4. There are many factors that affect oral medications (such as inability to swallow, chronic diarrhea and intestinal obstruction); 5. Patients with a history of CNS metastases or CNS metastases; 6. A history of bleeding, with any serious grading within 4 weeks prior to screening reaching a bleeding event of 3 degrees Celsius or greater in CTCAE4.0; 7. Serious infection; 8. Serious cardiovascular disease: uncontrolled hypertension, unstable angina, grade 3-4 heart failure (NYHA standard), congestive heart failure; 9. urinary routine urinary protein ≥ ++ and confirmed 24-hour urinary protein quantitation\> 1.0 g; 10. Within 30 days after major surgery; 11. Thrombotic disease. Anemia or venous thrombosis occurred in the previous year, such as cerebrovascular accident (including transient ischemic attack), deep vein thrombosis, pulmonary embolism, etc.; 12. Those with history of psychotropic substance abuse who can not be abstinent or have mental disorders; 13. Have clinical symptoms, need clinical intervention pleural effusion or ascites; 14. At the investigator's discretion, there is a serious concomitant condition that compromises the patient's safety or affects the patient in completing the study.