In this study, patients with middle or low rectal cancer will receive robotic radical resection, and will be randomly assigned to receive inferior mesenteric artery lymph nodes dissection or preservation. The 3-year disease-free survival rates of these two surgical approaches will be compared.

The goal of this clinical trial is to compare the outcomes of preserving versus dissecting inferior mesenteric artery root lymph nodes (IMA-LN) during robotic radical resection for mid/low rectal cancer. It aims to evaluate both short-term safety and long-term efficacy. The main questions it seeks to answer are:

1. Does preserving IMA-LN achieve non-inferior 3-year disease-free survival (DFS) compared to IMA-LN dissection?
2. Does preserving IMA-LN reduce postoperative complications (e.g., anastomotic leakage, urinary/defecation dysfunction) and improve quality of life?

Researchers will compare two surgical strategies:

1. IMA-LN preservation group: No dissection of IMA root lymph nodes, with ligation of the inferior mesenteric artery (IMA) distal to the left colic artery.
2. IMA-LN dissection group: Complete dissection of IMA root lymph nodes, with high or low ligation of the IMA.

Both groups will undergo robotic surgery following total mesorectal excision (TME) principles.

Participants will:

1. Be randomly assigned to either the preservation or dissection group. Receive standardized preoperative evaluations (imaging, biopsies) and postoperative follow-up for 3 years.
2. Undergo regular clinical assessments, including tumor marker tests, imaging (CT/MRI), colonoscopy, and quality-of-life questionnaires (evaluating urinary/sexual/defecation function).
3. Have surgical outcomes (e.g., complications, lymph node counts) and survival data recorded.

The trial aims to provide high-level evidence for optimizing surgical strategies in mid/low rectal cancer treatment.

Inclusion Criteria:

1. Age >18 years and ≤80 years
2. Pathologically confirmed rectal adenocarcinoma by colonoscopic biopsy
3. Tumor located ≤10 cm from the anal verge
4. No metastasis at the root of the inferior mesenteric artery (IMA) and no lateral lymph node metastasis confirmed by pelvic ultrasound, contrast-enhanced CT, and/or PET-CT (diagnostic criteria per the 2024 Chinese Society of Clinical Oncology [CSCO] Guidelines)
5. No distant metastasis (including pelvic, peritoneal, hepatic, pulmonary, cerebral, skeletal, or distant lymph node metastasis) confirmed by imaging
6. Pelvic MRI and/or transrectal ultrasound confirming cT1-T3 N0-1 stage, or ycT1-T3 Nx after neoadjuvant therapy (radiotherapy, chemotherapy, immunotherapy, targeted therapy)
7. No history of other malignancies (except adequately treated basal cell carcinoma or cervical carcinoma in situ)
8. Suitable for robotic surgery
9. Signed informed consent

Exclusion Criteria:

1. Clinical complete response after radiotherapy, chemotherapy, immunotherapy, or targeted therapy
2. cT1N0 tumors suitable for local excision
3. Emergency surgery required due to acute bowel obstruction, hemorrhage, or perforation
4. Multiple primary colorectal malignancies
5. Familial adenomatous polyposis (FAP), Lynch syndrome, or inflammatory bowel disease
6. Concomitant conditions requiring concurrent colonic resection
7. American Society of Anesthesiologists (ASA) grade >III
8. Pregnancy or lactation
9. Preoperative short-course radiotherapy
10. Inability of the patient/family to comprehend the study protocol

During the recruitment process, investigators will directly contact enrolled patients to avoid privacy breaches. All identity-related data will be stored separately in locked systems and de-identified. All researchers must refrain from disclosing patients' identifiable information.

De-identified patient data will be accessible to all investigators in this study and may be used for meta-analysis after audit and validation. Researchers should contact the principal investigator, Professor Jianmin Xu (xujmin@aliyun.com), to request data by providing a research proposal and institutional credentials. Requests will be reviewed and approved by the REAL2 trial's Independent Review Committee. Data will be available from the publication date until 36 months post-publication.

Data will be available from the publication date until 36 months post-publication.

De-identified patient data will be accessible to all investigators in this study and may be used for meta-analysis after audit and validation. Researchers should contact the principal investigator, Professor Jianmin Xu (xujmin@aliyun.com), to request data by providing a research proposal and institutional credentials.