Efficacy and safety of short-course radiotherapy in total neoadjuvant therapy combined with enlonstobart for pMMR locally advanced rectal cancer

Inclusion Criteria:

• 1.age >=18 years old, female and male. 2.Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 3.Histologically confirmed adenocarcinoma of the colon, and umor biopsy immunohistochemistry (IHC) indicates pMMR .

  4.Staged as T3-4 NanyM0 or T1-2N+ M0 according to the AJCC 8th edition. 5.Rectal cancer: <10 cm from the anal verge. 6.Adequate organ function:

  1. Hematology : i. Absolute Neutrophil Count (ANC) ≥ 1.5 × 10⁹/L. ii. Platelet count ≥ 100 × 10⁹/L . iii. Hemoglobin ≥ 90 g/L.

  2. Hepatic: i. Serum Total Bilirubin (TBil) ≤ 1.5 × ULN (Upper Limit of Normal). ii. AST and ALT ≤ 2.5 × ULN. iii. Creatinine ≤ 1.5 × ULN ; Renal: Calculated Creatinine Clearance (CrCl) ≥ 60 mL/min (calculated using the Cockcroft-Gault formula)

  3. Coagulation: i. International Normalized Ratio (INR) and Activated Partial Thromboplastin Time (APTT) ≤ 1.5 × ULN.

     7. Men and women of childbearing potential must agree to use effective contraceptive measures during the study and for 6 months after the last treatment.

     8. Willing and able to voluntarily provide written informed consent and comply with all scheduled treatments and follow-up assessments.

     Exclusion Criteria:

     1. Pathological diagnosis of other special types, including but not limited to neuroendocrine carcinoma or squamous cell carcinoma.
     2. Has previously received radiotherapy, targeted agents, or immune checkpoint inhibitors for the treatment of rectal cancer.
     3. Active autoimmune disease, such as systemic lupus erythematosus or rheumatoid arthritis, necessitating ongoing immunosuppressive treatment.
     4. Has active infection, including but not limited to HIV, or positive HBV/HCV viral load requiring antiviral therapy for control and stabilization.
     5. Significant cardiovascular disease, such as myocardial infarction within 6 months prior to enrollment, unstable angina pectoris, or hypertension that remains uncontrolled above 160/100 mmHg despite optimal therapy.
     6. History of other malignant tumors, excluding non-melanoma skin cancer and cervical carcinoma in situ that have been curatively treated and disease-free for ≥ 5 years.
     7. Uncontrolled diabetes (HbA1c > 8%) or thyroid dysfunction requiring medication for abnormal TSH.
     8. Severe chronic intestinal conditions，including but not limited to Crohn's disease or active ulcerative colitis.
     9. The investigators believe that patients were inappropriate for participation.