The present study is to develop the novel robotic surgical technique and enhance the surgery quality for the treatment of distal rectal cancer.

The intersphincteric resection (ISR) for the treatment of distal rectal cancer has been a complex two-step surgical procedure consisting of transabdominal mobilization of the anorectum and transanal bowel resection with handsewn coloanal anastomosis. The availability of robotic systems may facilitate the transabdominal approach, simplify the surgical procedures, and achieve better anorectal function for patients with distal rectal cancer requiring an ISR. Consecutive 40 patients with distal rectal cancer undergoing the single-step robotic transabdominal ISR with the intent-to-treat principle will be recruited. The risk factors for a failed transabdominal ISR were identified from the prospectively maintained clinicopathologic data using univariate and multivariate analysis. The surgical outcomes, the anorectal function, and the tumor recurrence were compared between patients with a successful or failed robotic transabdominal ISR. The investigators believe that the present project can facilitate the development of the novel robotic surgical technique and enhance the surgery quality for the treatment of distal rectal cancer in our hospital and even in Taiwan.

Inclusion Criteria:

• cT1-3 or yT 1-3 rectal adenocarcinoma whose low border was located below the anorectal sling (4 cm from anal verge), in which the required surgery meets the definition of ISR;
• Clinically Tumor-Node-Metastasis (TNM) stage I-III rectal adenocarcinoma;
• Curative and elective surgery;
• American Society of Anesthesiology (ASA) class Ⅰ to Ⅲ patients;
• Age between 20 and 75 years.

Exclusion Criteria:

• cT4 adenocarcinoma, i.e., the rectal cancer invaded to external sphincter or adjacent pelvic organs;
• Evidence of distant metastasis;
• Primary tumor mass≧8 cm in diameter;
• Morbidly obese patients, i.e., body mass index (BMI) ≧ 40 kg/m2 ;
• Previous major surgery of low upper abdomen;
• The adenocarcinoma has invaded to lateral pelvic side wall requiring a lateral pelvic lymph node dissection. (7) Patients with poor anorectal function (Wexner incontinence Score≧ 10)

The patients diagnosed as rectal cancer and met with the above inclusion and exclusion criteria will be recruited.