To Explore a Single-arm Phase II Study on Intestinal Microbiota Transplantation Combined With Neoadjuvant Immunotherapy and Chemoradiotherapy for Locally Advanced Rectal Cancer Under MSS/pMMR

Inclusion Criteria:

1. ECOG PS 0-1
2. The lower edge of the tumor is ≤12cm from the anal margin. After multidisciplinary assessment, R0 resection is possible
3. RAS/BRAF wild type, pMMR/MSS status
4. Patients of childbearing age need to take effective contraceptive measures.
5. Voluntarily sign the informed consent form

Exclusion Criteria:

1. dMMR/MSI-H type
2. Has previously received anti-tumor treatment (including surgery, radiotherapy, chemotherapy, targeted therapy or immunotherapy);
3. Active autoimmune diseases, inflammatory bowel disease;
4. Active infection, immune deficiency, severe liver and kidney dysfunction;
5. Severe intestinal obstruction, perforation or requiring emergency surgery;
6. Pregnant or lactating women;
7. Contraindications related to FMT (such as recent use of high-dose immunosuppressants, severe neutropenia, etc.);
8. Other circumstances where participation in clinical trials is not suitable