• Age ≥18 years old and ≤75 years old

• Histologically confirmed colorectal adenocarcinoma

• Radiologically and/or pathologically confirmed liver metastasis

• Immunohistochemistry and/or genetic testing confirmed pMMR/MSS

• Absence of extrahepatic metastasis confirmed by CT, MRI or PET/CT (if necessary)

• Primary lesion has been or can be removed by radical surgery

• Liver metastases can be resected (or using intraoperative radiofrequency) and is expected to achieve tumor-free status (NED) after surgery. Resectable liver metastases are defined explicitly as ① less than 5 metastatic lesions; ② R0 resection is achievable by resection or intraoperative radiofrequency; ③ Remaining liver volume is expected to be sufficient after surgery; ④ The following can be retained after resection: One hepatic vein, preserve blood flow in and out of the remaining liver, the bile duct, and at least 2 adjacent livers segments ⑤ There is no extrahepatic metastasis.

• Apart from surgical resection of the primary lesion, he/she has not received any anti-tumor treatment for liver metastasis (including chemotherapy, targeted drugs, interventional therapy, immunotherapy, radiotherapy, etc.)

• Normal hematological function (platelets\>90×109/L; white blood cells\>3×109/L; neutrophils\>1.5×109/L)

• Serum bilirubin ≤ 1.5 times the upper limit of normal (ULN), transaminase ≤ 5 times ULN, alkaline phosphatase ≤2.5 ULN, No ascites, normal coagulation function, albumin ≥35g/L

• Child-Pugh classification of the liver is A

• Serum creatinine is less than the upper limit of normal (ULN), or the calculated creatinine clearance rate is greater than 50ml/min (using Cockcroft-Gault formula)

• ECOG score 0-1

• Life expectancy\> 3 months

• Signed and written informed consent

• Willing and able to follow up until death or the end of the study or the study is terminated