Rectal Artery Infusion Chemotherapy Combined With Anti-PD1 Antibody for MSS LARC

Inclusion Criteria: * Pathologically diagnosed rectal adenocarcinoma * Age ≥18 years old and ≤75 years old * MRI stage T3-4aNany and TanyN1-2, but not T4b and no distant metastasis * Life expectancy of 1 year The above * Informed consent, no contraindications to chemotherapy exist * The distance from the lower edge of the tumor to the anus is between 5cm to 12cm by MRI Exclusion Criteria: * Refused to participate in this study * Multifocal colorectal cancer * Past history of malignant tumors, except for basal cell carcinoma/papillary thyroid carcinoma/various types of carcinoma in situ * Unable to receive chemotherapy , such as but not limited to bone marrow suppression, etc * Major organ diseases (such as but not limited to COPD, coronary heart disease and renal insufficiency, etc.) acute attack and or severe acute infectious diseases (such as but not limited to hepatitis, pneumonia and myocarditis, etc.), ASA score\> 3 * Mental disorder or illiteracy or language and communication barriers cannot understand the research plan * There are contraindications to arterial puncture, such as but not limited to severe arteriosclerosis or even atresia, coagulation dysfunction, long-term use of anticoagulant drugs and cannot be stopped, etc * Rectal tumor has obstruction or high risk of obstruction and or there is bleeding and/or perforation * Peripheral sensory nerve disorder, unable to receive oxaliplatin chemotherapy * Lateral pelvic lymph node metastasis (mainly supplied by inte…