Total Neoadjuvant Therapy With PD-1 for Locally Advcancer Rectal Cancer

Inclusion Criteria:

1. Pathologically confirmed rectal adenocarcinoma;
2. Mid-low rectal cancer, with the lower edge of the tumor located within 12 cm from the anal verge;
3. Magnetic resonance imaging (MRI) suggests locally advanced rectal cancer (T3 or T4 and M0), accompanied by at least one of the following risk factors: cT4, N2, lymphovascular invasion, involvement of the mesorectal fascia, or enlarged lateral lymph nodes (short-axis diameter \> 8 mm); patients with potentially resectable disease;
4. Polymerase chain reaction (PCR) testing indicates microsatellite stability (MSS) type;
5. No prior antitumor therapy, such as chemotherapy, radiotherapy, immunotherapy, or targeted therapy;
6. Age between 18 and 75 years;
7. ECOG Performance Status (PS) score of 0-1;
8. Laboratory test results: WBC ≥ 3.5 × 10\^9/L, Hb ≥ 100 g/L, PLT ≥ 100 × 10\^9/L; normal liver and kidney function;
9. Absence of severe comorbidities, and ability to tolerate surgical treatment;
10. The patient or their immediate family member voluntarily agrees to participate in this study and provides written informed consent.

Exclusion Criteria:

1. Recurrent rectal cancer;
2. Synchronous colorectal cancer;
3. Pregnant or lactating patients;
4. History of other malignant tumors;
5. Previous antitumor therapy, including chemotherapy or radiotherapy;
6. Dysfunction of vital organs such as cardiac or pulmonary insufficiency;
7. History of autoimmune diseases or immunodeficiency disorders;
8. Use of immunosuppressive drugs within the past year;
9. Distant metastasis to organs such as the abdominal cavity, pelvis, liver, or lungs;
10. Active bleeding;
11. Tumor involvement of adjacent structures such as the prostate or sacral organs, making the tumor unresectable;
12. Allergy to chemotherapeutic agents, immune checkpoint inhibitors, or cetuximab;
13. Psychiatric disorders or lack of capacity for civil conduct, unable to provide informed consent.