The objective is to investigate the efficacy and safety of two-weekly alternative regimen of Bevacizumab plus XELOX/XELIRI for First-line Treatment in Unresectable Advanced Colorectal Cancer.

XELOX is a commonly used chemotherapy regimen, and XELIRI has also been widely used in the second-line treatment. XELOX and XELIRI adopt the three-week regimen, and the single dose of oxaliplatin and irinotecan is large, which has a great impact on the gastrointestinal toxicity and blood toxicity of patients. Therefore, there is no lack of a two-week improved regimen with increased frequency and reduced single dose applied in clinical, so that it has good safety, exact efficacy and increase the drug delivery density. Based on the above, we should not only consider the efficiency of the three drugs, but also control the toxic reaction. The objective is to evaluate the efficacy and safety of two-weekly alternative regimen of Bevacizumab plus XELOX/XELIRI for First-line Treatment in Unresectable Advanced Colorectal Cancer.

Inclusion Criteria:

1. 18-75 years old;
2. Patients with advanced colorectal adenocarcinoma diagnosed by histopathology, or with metastasis more than 12 months after radical operation, and the metastasis could not be removed;
3. ECOG score ≤ 2, estimated survival time ≥ 3 months;
4. Leucocytes ≥ 3.5 × 109 / L, neutrophils ≥ 1.5 × 109 / L, hemoglobin ≥ 100g / L, platelets ≥ 80 × 109 / L, serum liver enzyme in patients without liver metastasis is not higher than 2.5 times of the upper limit of normal value, serum liver enzyme in patients with liver metastasis is not higher than 5 times of the upper limit of normal value, serum bilirubin level is not higher than 1.5 times of the upper limit of normal value, serum creatinine level is not higher than 1.5 times of the upper limit of normal value;
5. At least one lesion can be measured by CT or MRI;
6. No other history of malignant tumor;
7. Those who are fertile but willing to take contraceptive measures;
8. Sign the written informed consent.

Exclusion Criteria:

1. Patients with allergic, hypersensitive constitution and autoimmune diseases;
2. There are only unmeasurable lesions, such as hydrothorax and ascites, carcinomatous lymphangitis, diffuse liver invasion and bone metastasis; No measurable or non assessable lesions;
3. Pregnant or lactated women;
4. Uncontrolled symptomatic brain metastasis or mental disorder can not correctly describe subjective symptoms;
5. Major organ failure;
6. Affecting drug administration, absorption, distribution, metabolism, excretion, etc. the patient has uncontrollable epileptic attack, central nervous system disorder or loss of self-knowledge due to mental disease, physiological or pathological malnutrition, chronic diarrhea, and cachexia;
7. Patients with complete or incomplete ileus；
8. Patients with serious heart disease or history, including documented history of congestive heart failure, high-risk uncontrolled heart rate disorder, angina requiring drug treatment, clinically clear history of heart valve disease, serious myocardial infarction and stubborn hypertension;
9. Severe uncontrollable infection;
10. Alcohol and /or drug abuse or poor compliance of the investigator's judgment.