Neoadjuvant Toripalimab With or Without Celecoxib in dMMR/MSI-H Colorectal Cancer

Inclusion Criteria: 1. Willing and able to provide written informed consent. 2. Histological or cytological documentation of adenocarcinoma of the colon or rectum. 3. Tumor tissues were identified as mismatch repair-deficient (dMMR) by immunohistochemistry (IHC) method or microsatellite instability-high (MSI-H) by polymerase chain reaction (PCR). 4. Male or female subjects aged 18 to 75 years. 5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 6. Determined CT or MRI scans (done within 14 days of registration) of the chest, abdomen and pelvis: locally advanced (cT3-4 or cN1-2 \[with the definition of a clinically positive lymph node being any node ≥ 1.0 cm\]). 7. Non complicated primary tumor (obstruction, perforation, bleeding). 8. No previous any systemic anticancer therapy for colorectal cancer disease. 9. Adequate bone marrow, hepatic and renal function as assessed by the following laboratory requirements conducted within 7 days of starting study treatment. Exclusion Criteria: 1. Previous or concurrent cancer that is distinct in primary site or histology from colorectal cancer within 5 years prior to randomization. 2. Significant cardiovascular disease including unstable angina or myocardial infarction within 6 months before initiating study treatment. 3. Heart failure grade III/IV (NYHA-classification). 4. Unresolved toxicity higher than CTCAE v.4.0 Grade 1 attributed to any prior therapy/procedure. 5. Subjects with known allergy to the study drugs or to any of its excipients. 6. Current or recent (within 4 weeks prior to starting study treatment) treatment of another investigational drug or participation in another investigational study. 7. Breast- feeding or pregnant women 8. Lack of effective contraception. 9. Previously received anti-programmed death-1 (PD-1) or its ligand (PD-L1) antibody, anti-cytotoxic T lymphocyte-associated antigen 4 (cytotoxic T-lymphocyte-associated Protein 4, CTLA-4) antibody or other drug/antibody that acts on T cell costimulation or checkpoint pathways. 10. With any distant metastasis.