This trial is a single-center retrospective study. Eligible patients receiving PD-1 inhibitor treatment will enrolled.

In patients with colorectal cancer (CRC), curative surgery combined with chemotherapy ( FOLFOX or CAPOX regimens) has become the standard treatment. However, 20 to 30% of these patients will develop distant metastasis, which ultimately results in death. Oxaliplatin- and fluoropyrimidine-based doublet chemotherapy does not adequately meet the clinical need for tumor shrinkage and downstaging. There is an urgent need to explore drugs with different mechanisms of action in combination with chemotherapy to improve efficacy. Relatively few trials of preoperative therapy have been reported, In recent years, the emergence of immune checkpoint inhibitors has revolutionized cancer treatment. Given the limitations of current treatment strategies in achieving optimal clinical outcomes, this retrospective study aims to research the disease-free survival rates and overall survival (OS) in CRC patients using PD-1 inhibitors.

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Inclusion Criteria:

Willing and able to provide written informed consent. Histological or cytological documentation of adenocarcinoma of the colorectal. Eastern Cooperative Oncology Group's (ECOG) performance status of 0 or 1. CT or MRI scans (done within 30 days of registration) of the chest, abdomen, and pelvis all without clear evidence of distant metastatic (M1) disease.

No clinically significant obstruction, perforation, or bleeding related to the primary tumor.

No previous systemic anticancer therapy for colon cancer disease. Adequate bone marrow, hepatic, and renal function as assessed by the following laboratory requirements conducted within 7 days of starting the study treatment

Exclusion Criteria:

Previous or concurrent cancer that is distinct in primary site or histology from colon cancer within 5 years before randomization.

Significant cardiovascular disease including unstable angina or myocardial infarction within 6 months before initiating study treatment.

Heart failure grade III/IV (NYHA classification). Unresolved toxicity higher than CTCAE v.5.0 Grade 1 attributed to any prior therapy/procedure.

Subjects with known allergy to the study drugs or any of its excipients. Current or recent (within 4 weeks before starting study treatment) treatment of another investigational drug or participation in another investigational study.

Breast-feeding or pregnant women Lack of effective contraception.

CRC patients receiving PD-1 inhibitors