Effectiveness Study of Resection of Primary Tumor in Stage IV Colorectal Cancer Patients

Inclusion Criteria: * 18 to 70 years old * both genders * ECOG:0-2 score * Pathological confirmed colon cancer or rectal cancer with at least 12 cm far away from anal verge * CT,MRI,or PET-CT confirmed metastasis * MDT confirmed unresectable metastasis lesion * No evidence of obstruction, bleeding, perforation * WBC≥4.0×109/L，Neu ≥2.0×109/L，PLT≥100×109/L * No contraindication for chemotherapy * No evidence of other malignant tumor * Expected survival time \> 6 months Exclusion Criteria: * mCRC patients who did not respond to first line chemotherapy * Require surgical intervention during the primary tumor-related symptoms * Obvious coagulopathy * Severe heart, liver, kidney damage or other serious uncontrolled medical illness or acute infection, cachexia * Severe organ damage after chemotherapy, surgery or unable to continue to systemic chemotherapy * Pregnant or lactating women or women of childbearing age who refuse to accept contraception. * Nearly three months participated in clinical trials of other persons. * Mental abnormalities