Approximately one third of patients with colorectal cancer are diagnosed as locally advanced stage with metastasis to N3 - N4 lymph nodes requiring a D3 - D4 lymphadenectomy. Our previous study has indicated that, by laparoscopic approach, the extended abdomino-iliac lymphadenectomy, the so-called D3-D4 lymph node dissection, could be performed with quick convalescence and similar oncologic efficacy for the treatment of advanced recto-sigmoid cancer with metastatic lesions over N3-N4 lymph nodes, as compared with traditional open surgery. In the present study, the investigators will further compare the oncologic and functional outcomes of robotic versus laparoscopic approach in performing such challenging surgical procedures for patients with advanced colorectal cancer requiring a D3-D4 lymphadenectomy through a randomized prospective clinical trial.

Approximately one third of patients with colorectal cancer are diagnosed as locally advanced stage with metastasis to N3 - N4 lymph nodes requiring a D3 - D4 lymphadenectomy. Our previous study has indicated that, by laparoscopic approach, the extended abdomino-iliac lymphadenectomy, the so-called D3-D4 lymph node dissection, could be performed with quick convalescence and similar oncologic efficacy for the treatment of advanced recto-sigmoid cancer with metastatic lesions over N3-N4 lymph nodes, as compared with traditional open surgery. In the present study, the investigators will further compare the oncologic and functional outcomes of robotic versus laparoscopic approach in performing such challenging surgical procedures for patients with advanced colorectal cancer requiring a D3-D4 lymphadenectomy through a randomized prospective clinical trial.

In the upcoming three years (2020/4/1-2023/3/31),consecutive recto-sigmoid cancer patients with metastasis to para- aortic lymph node will be screened and randomized to patient groups undergoing either robotic or laparoscopic D3-D4 lymph node dissection. The extent of D4 lymph node dissection includes extirpation of the extra-mesenteric lymphatic basin along bilateral common iliac arteries and veins, inferior vena cava, and abdominal aorta upward to the level just below the duodenal third portion and left renal vein, besides the traditional mesenteric dissection of paracolic (N1) lymph nodes, intermediate (N2) mesenteric lymph nodes, and lymph nodes around the root of inferior mesenteric artery (N3). The harvested lymph nodes were mapped and managed according to the Japanese guidelines. The metrics of surgical outcomes included: the number of harvested lymph nodes; time to recurrence of cancer after surgery; the length of operation time; blood loss; intra-operative and post-operative complications; and wound size. Functional recovery was evaluated by length of post-operative flatus passage, the restoration of urinary function, hospitalization, and degree of post-operative pain. A subjective-response standardized questionnaire was given to patients to assess disability, which included the number of days until return to partial activity, full activity, and work.

Since the current randomized prospective study in this field is still lack of, the investigators believe that this study will be of academic importance. And, clinically, the presented study can to help set up the standard operation procedures for such patient, and provide the level one evidence for National Health Insurance Administration in evaluating the reimbursement of HTA (high technology assessment) procedures.

Inclusion Criteria:

• Histopathologically proved adenocarcinoma located at upper rectum (above pelvic peritoneal reflection), recto-sigmoid junction, or distal sigmoid colon (generally 10 to 25 cm above anal verge). Only recto-sigmoid cancers above the peritoneal reflection were investigated because the lymphatic drainage of upper rectum and distal sigmoid colon was along the inferior mesenteric artery to the para-aortic area, and therefore the extent of surgical resection and lymph node mapping were standardized.
• Clinically TNM stage III cancers.
• Curative robotic or laparoscopic surgery.
• American Society of Anesthesiology (ASA) class I to III patients.
• Age between 50 and 75 years. This was because patients >50 years old are generally deemed to be over the reproductive age, and the D3 dissection was considered too aggressive for patients older than 75 years.
• Patients who are willing to receive minimally invasive surgical procedures to treat their rectosigmoid cancer.

Exclusion Criteria:

• Tumors located at other anatomic positions;
• Emergency or palliative surgery;
• Evidence of disseminated disease or adjacent organ invasion;
• Primary tumor mass ≥8 cm in diameter;
• Morbidly obese patients (body mass index ≥40 kg/m2);
• Previous major surgery of lower abdomen.

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