Neoadjuvant Therapy for Locally Advanced Rectal Cancer

Inclusion Criteria: -Patient's age: 18 years old - 80 years old - * Rectal cancer patients diagnosed with adenocarcinoma by pathological examination of primary biopsy * Patients with no prior treatment, preoperative clinical stage: cT3-4N+M0 rectal cancer patients (AJCC 8th); * Patients who agree to undergo radical surgical treatment and have no contraindications to surgery as judged by the surgeon; * No other multiple primary cancers; * At least 1 measurable or evaluable lesion according to the efficacy evaluation criteria for solid tumors version 1.1 (RECIST v1.1); * Expected survival time≥ 3 months; * A score of 0-1 based on the United States Eastern Cooperative Oncology Group Performance Status Score (ECOG PS score); * The investigator plans to give PD-1 monoclonal antibody combined with chemotherapy treatment regimen after evaluation, and signs informed consent. Exclusion Criteria: * Active, known or suspected autoimmune disease; * Known history of primary immunodeficiency; * Known history of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation; * Pregnant or lactating female patients; * Patients with intestinal obstruction, intestinal perforation, intestinal bleeding, etc., requiring emergency surgery; * Uncontrolled intercurrent illness including but not limited to: * People living with HIV (HIV antibody positive) * Severe infections that are active or poorly clinically controlled * Patients with active hepatitis * Evidence of severe or uncontrolled systemic disease (e.g., severe psychiatric, neurological, epilepsy or dementia, unstable or incompensable respiratory, cardiovascular, hepatic or renal disease, uncontrolled hypertension \[i.e., greater than or equal to CTCAE grade 2 hypertension despite medication\]). * Patients with active bleeding or new thrombotic disease, taking therapeutic dose of anticoagulant drugs or bleeding tendency, abnormal coagulation function (INR\>1.5×ULN, APTT\>1.5×ULN); * Those who are currently undergoing clinical trials of other drugs; * Other patients who are considered by the investigator to be unsuitable for inclusion.