Total Meso-rectal Excision Versus Transanal Local Excision Followed by Radiotherapy for T2N0M0 Distal Rectal Cancer

Rectal cancer is one of the most common malignancy worldwide. Currently, surgery is the main treatment for stage I rectal cancer, which has good therapeutic effect. For ultra-low rectal cancer, transanal endoscopic microsurgery (TEM) has many advantages over total mesorectal excision (TME), such as less trauma, shorter hospitalization time, lower incidence of complications, protection of sexual function and protection of anal function. At present, transanal local excision has become the recommended operation for the T1N0M0 rectal cancer. However, the risk of lymph node metastasis still occurs in stage I tumors, especially in stage T2 tumors, the lymph node metastasis rate can reach 12% - 29% according to the literature. Salvage TME or chemoradiotherapy should be considered for the presence of positive margin of incision, lymphatic/vascular invasion and poor histological differentiation after transanal local excision. At present, the investigators have consulted a large number of literatures and found that TEM is still lack of sufficient evidence in the treatment of T2N0M0 ultra-low rectal cancer. Some studies believed that local excision combined with adjuvant therapy is safe and reliable, but the evidence is not enough. For ultra-low T2N0M0 rectal cancer, more studies need to be carried out to provide guidance for clinical treatment.

In this study, eligible patients will be randomly allocated to operative operation for rectal cancer either by TEM following radiotherapy or TME. 3-years local recurrence rate, 3-years disease free survival rate and 3-years overall survival rate，and postoperative quality of life will be recorded. Patients will be followed up every 3 months for 2 year, every 6 months for 3 years postoperatively to study the long term effects.

Inclusion criteria

• Age between 18 and 75 years.
• Histologically confirmed adenocarcinoma by preoperative biopsy.
• Tumor located within 4 cm from the anal verge, confirmed by at least one of the following methods: digital rectal examination, pelvic magnetic resonance imaging (MRI), or colonoscopy.
• Tumor size ≤3 cm, without fixation and with preserved mobility on clinical examination.
• Clinical stage T2 rectal cancer confirmed by preoperative high-resolution pelvic MRI.
• No radiological evidence of suspicious lymph node metastasis or distant metastasis on preoperative contrast-enhanced computed tomography (CT) and MRI.
• Ability to provide written informed consent.

Exclusion criteria

• History of other malignant tumors within the past 5 years.
• Poorly differentiated adenocarcinoma, mucinous adenocarcinoma, or signet ring cell carcinoma confirmed by pathological examination.
• Multiple primary colorectal tumors.
• Pregnant or breastfeeding women.
• Patients with plans for pregnancy.
• Severe psychiatric disorders.
• Previous treatment for rectal cancer, including radiotherapy or chemotherapy.
• Concomitant intestinal diseases, including familial adenomatous polyposis (FAP), hereditary nonpolyposis colorectal cancer (HNPCC), active ulcerative colitis, or Crohn's disease.
• Poor general condition or uncontrolled serious comorbidities that may affect study participation or treatment.
• Contraindications to laparoscopic surgery, including extensive intra-abdominal adhesions caused by previous abdominal surgery or inability to tolerate pneumoperitoneum.
• Current participation in another clinical trial.