RALOX or CAPOX + Bevacizumab in the First-line Treatment of Advanced CRC(ROCB Study)

According to the inclusion and exclusion criteria, the patients will be randomly divided into two groups: the experimental group (group A) will be administered with raltitrexed 3mg/m2 intravenously combined with oxaliplatin and bevacizumab, repeated every 21 days. The control group (group B) will be administered with orally capecitabine (1000mg/m2, d 1-14) combined with oxaliplatin and bevacizumab, repeated every 21 days. After 8 cycles of treatments, if evaluated as complete response(CR),partial response(PR) or stable disease(SD), CRC patients will go into maintenance therapy wtih raltitrexed combined with bevacizumab in group A or capecitabine combined with bevacizumab in group B respectively, ended in disease progression(PD) , symptoms deterioration, unacceptable toxicity, death or withdrawal of consent (whichever occurs first). The radiological efficacy will be evaluated every 6 weeks (2 treatment cycles) and non-PD (PD criteria referring to RECIST 1.1 criteria) patients will continue to be treated until the cancer progression or the patient's intolerable toxicity or death. Toxic side effects and quality of life will be assessed at the same time. Follow up participants and analyse primary endpoint (PFS) and secondary endpoints (OS,ORR and DCR).The causes of confirmed missing data in the trial should be recorded in detail to determine the mechanism of missing data and choose the suitable missing data handling methods.