• Signed written informed consent and volunteered to participate in the study;

• Age 18-75 years old (including the cut-off value), male or female;

• Locally advanced rectal adenocarcinoma confirmed by histopathology;

• High risk on pelvic MRI \[one of the following criteria\] :

‣ Clinical tumor (cT) stage cT4a or cT4b (according to the AJCC, 8th edition)

⁃ Extramural vascular infiltration

⁃ Clinical lymph node (cN) stage cN2 (according to the AJCC, 8th edition)

⁃ Involvement of the mesenteric fascia

⁃ Enlarged lateral lymph nodes

• The distance between the lower edge of the tumor and the anal edge is ≤10cm;

• Able to swallow tablets and capsules normally;

• ECOG PS 0-1

• Have not received any anti-tumor treatment for rectal cancer, including surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapy, etc.

• Plan to undergo surgery after completion of total neoadjuvant therapy;

⁃ No surgical contraindications;

⁃ Normal major organ function, including:

• Routine blood test (no blood transfusion and blood products within 14 days prior to the first treatment, no correction with G-CSF and other hematopoietic stimulating factors) :

‣ Neutrophil count ≥ 1.5×109/L

⁃ Platelet count ≥ 100×109/L

⁃ Hemoglobin ≥ 90 g/L

⁃ White blood cell count ≥ 3.0×109/L

∙ Blood biochemical tests:

‣ Total bilirubin ≤ 1.5×ULN (Gilbert's syndrome subjects, ≤3×ULN; Tumor liver metastasis, total bilirubin ≤3×ULN)

⁃ ALT ≤ 2.5×ULN, AST ≤ 2.5×ULN (≤5×ULN for patients with liver metastases)

⁃ Serum creatinine ≤ 1.5×ULN, or creatinine clearance ≥ 50 mL/min (Cocheroft-Gault formula, see Annex 2)

∙ Coagulation function:

‣ International Normalized ratio (INR) ≤ 1.5×ULN

⁃ Activated partial thromboplastin time (APTT) ≤ 1.5×ULN

⁃ Prothrombin time (PT) ≤1.5×ULN

∙ Doppler ultrasound assessment: left ventricular ejection fraction (LVEF)≥50%

⁃ Female subjects of childbearing potential were required to have a negative serum pregnancy test within 14 days before starting the trial drug and to have used an effective contraceptive method (e.g., an intrauterine device, contraceptive pill, or condom) during the trial and for at least 6 months after the last dose; Male participants whose partner is a woman of childbearing potential should use effective contraception during the trial and for 6 months after the last dose;