Neoadjuvant Safety of Sintilimab + XELOX + Bevacizumab in PMMR/MSS CRLM Patients

Inclusion Criteria: * 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-Pug…