Tyrosine Kinase Inhibitor (TKI) + Anti-PD-1 Antibody in TKI-responded Microsatellite Stability/Proficient Mismatch Repair (MSS/pMMR) Metastatic Colorectal Adenocarcinoma.

Inclusion Criteria: * Subjects who voluntarily participated in the study, signed the written informed consent form, and could comply with the protocol of study. * Male or female of age 18-75 years. * Subjects with colorectal adenocarcinoma who were histopathologically confirmed, and with locally advanced (unresectable) or mCRC. * Subjects who underwent standard antitumor therapies (fluorouracil, oxaliplatin, irinotecan were used, with or without administration of bevacizumab and/or cetuximab). * Patients with MSS/pMMR mCRC (immunohistochemistry, polymerase chain reaction or next-generation sequencing can be used). * All adverse reactions associated with drug use or surgery were reduced to grade 0-1 (according to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0) or to a level required by the protocol criteria. * The presence of at least one measurable lesion by computed tomography (CT) or magnetic resonance imaging (MRI). * Eastern Cooperative Oncology Group (ECOG) performance status score of ≤ 1. * Subjects with life expectancy ≥ 12 weeks. * Adequate important organs functions: bone marrow function (neutrophil count ≥ 1.5×10\^9/L; platelet ≥ 80×10\^9/L; hemoglobin ≥ 90 g/L), liver function (serum albumin ≥ 28 g/L; total bilirubin ≤ 1.5×upper limit of normal (ULN); alanine aminotransferase and aspartate aminotransferase ≤ 3×ULN, or ≤ 5×ULN if liver metastases are present), renal function (serum creatinine ≤ 1.5×ULN or creatinine clearance (CrCl) ≥ 40 mL/min,…