Compare Efficacy and Safety of Raltitrexed-based and 5fu-based Neoadjuvant Chemotherapy for Colorectal Liver Metastasis

Inclusion Criteria: 1. Histologically confirmed chinese colorectal cancer patients and imaging detection confirmed liver metastasis 2. previously no treatment for liver metastasis or Primary tumor had been removed and last additional chemotherapy over one year 3. Age of≥18 and ≤75 4. Adequate organ functions, as determined by normal bone marrow function (absolute neutrophil count2 x 109/L, platelets 100 x 109/L, White blood cells 4 x 109/L), liver function (serum bilirubin ≤ 2.5 x ULN, serum transaminases ≤2. 5x ULN) 5. ECOG≤1 6. Life Expectancy\>6months 7. Signed written informed consent 8. Expected adequacy of follow-up Exclusion Criteria: 1. Lesion is too small to assess by imaging 2. Extrahepatic metastases 3. Any anticancer chemotherapy in development within 4 weeks prior to study entry 4. Concurrent uncontrolled illness such as infection 5. Be allergic to medicines in the study 6. Pregnant or nursing patients 7. Fertile women (\< 2 years after last menstruation) and men of childbearing potential not willing to use effective means of contraception. 8. Not willing or incapable to comply with all study visits and assessments 9. Evidence of any other disease, metabolic dysfunction, physical examination finding or laboratory finding giving reasonable suspicion of a disease or condition that puts the patient at high risk for treatment-related complications.