Apatinib Versus Bevacizumab in Second-line Therapy for Colorectal Cancer(ABST-C)

Firstly, screen eligible mCRC patients for enrolment. Our CRC clinical nurse specialists will document medical history of patients including diagnoses, first-line chemotherapy (mFOLFOX6 or CAPOX),bevacizumab dosage,toxicities,PFS on previous therapy.In the meantime,chest-abdonimal-pelvic CT and blood tests are to be examined to assess base-line measurable lesions and guarantee adequate organ function prior to enrolment.If all the values meet the criteria for enrolment, consent will be signed. Secondly, randomise patients into two arms: Arm A-apatinib plus FOLFIRI regimen and arm B-bevacizumab plus FOLFIRI regimen.A software which is alike the procedure of coin flipping is used to randomise eligible patients.According to the selected regimen in specific arm,patients will be given full-dose drugs or reduced dose drugs if serious toxicities ( CTCAE v4.0 criteria grade 3/4) are complained since previous cycle of treatment.Symptoms and blood test results (including CEA and CA199) before each cycle will be recorded and the consultant oncologist, who is responsible for individual participants, will decide whether to continue next cycle chemotherapy with apatinib or bevacizumab based on the assigned arm.Radiological assessment consisting of chest-abdonimal-pelvic CT will be performed every 2 months.Notably,the monitor will check with physicians and nurse specialists for the accuracy and completeness of all data. Thirdly, follow up participants and analyse primary end point (PFS) and secondary end points (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.