We reviewed the prospectively collected records of patients with mid or low rectal cancer after preoperative CRT who underwent robotic surgery at the National Cancer Center between March 2010 and January 2012. The inclusion criteria were as follows: histologically proven adenocarcinoma located ≤ 9 cm from the anal verge; locally advanced rectal cancer (cT3N0-2) treated with preoperative CRT; no previous or concurrent malignancy at another site; and no evidence of distant metastasis at the time of surgery. We identified and matched 33 patients (1:2) with 66 patients who underwent laparoscopic surgery. Matching criteria included patient age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, tumor stage, and CRT method (long course vs. short course). Patients with a histological diagnosis other than adenocarcinoma, familial adenomatous polyposis, or hereditary nonpolyposis colorectal cancer were excluded.

Tumor location was defined as the distance between the distal margin of the tumor and the anal verge as measured using rigid sigmoidoscopy and a digital rectal examination. The tumor stage was recorded postoperatively according to the American Joint Committee on Cancer staging system. The tumor response to CRT was described according to the tumor regression grade scale proposed by Dworak et al. [14]. Use of the robot versus laparoscopy was based on the surgeon’s clinical decision and patient preference. As robotic surgery has been suggested to have benefits in surgeries performed in a narrow space, surgeons considered the robotic surgery for patients with a narrow pelvis and low lying rectal cancer after CRT. The patients were given a full explanation of the costs and possible benefits of robotic surgeries and underwent robotic surgery under their consent. This study protocol was approved by Institutional Review Board of National Cancer Center (NCCNCS-12-609).

Patients were preoperatively staged by endorectal ultrasound, magnetic resonance imaging, computed tomography (CT) and positron emission tomography. Preoperative concurrent chemotherapy was administered to all patients following a 5-fluorouracil–based regimen. Long-course CRT was delivered to the entire pelvis at a dose of 45 Gy in 25 fractions, followed by 5.4 Gy in 3 fractions within 6 weeks. Short-course CRT consisted of a total dose of 25 Gy with daily fractions of 5 Gy for 5 days. The intervals between CRT completion and operation were 6 to 8 weeks in patients with long-course CRT and 4 to 8 weeks in those with short-course CRT. A prospective study investigating the efficacy of delayed surgery after short-course CRT had been conducted in our center between February 2010 and October 2011 [15], of which patients were included in this study. In consequence, surgery after short-course CRT was performed in 4 to 8 weeks.

The perioperative clinical outcomes were recorded and analyzed. The operation time was recorded from the start of the operation to the time of wound closure. Anastomotic leakage was defined as peritonitis confirmed through clinically apparent leakage (discharge from the pelvic drain containing pus or fecal material) or radiological evidence (a complicated fluid collection or an abscess on CT scan or rectal water-soluble contrast study). In the pathologic data, the circumferential resection margin (CRM) was considered positive when the distance between the tumor and the proper rectal fascia was ≤ 1 mm. TME quality was classified macroscopically as complete, nearly complete, or incomplete [16].

Robot-assisted surgery was performed using a da Vinci S Surgical System (Intuitive Surgical Inc., Sunnyvale, CA). The patient was placed in the modified Lloyd-Davis position. We performed total robot-assisted surgery without changing the position of the robotic cart, but the robotic arms were repositioned for the pelvic TME procedure as described by Choi et al. [17]. We used a six-port system. One 12-mm port was inserted for the 30° camera approximately 2 cm right and lateral to the supraumbilical area. Four 8-mm ports were used for the robotic arms and placed in the following locations: the McBurney point; the right subcostal area on the midclavicular line (MCL); the left subcostal area, approximately 2-cm medial to the MCL; and the counter-McBurney point. One additional 5-mm port between the first and second 8-mm ports was used by the surgical assistant.

The surgical technique was standardized as follows. First, the inferior mesenteric vein was divided adjacent to the fourth portion of the duodenum. The inferior mesenteric artery was then ligated and the sympathetic para-aortic nerve plexus and superior hypogastric nerve were preserved. Colonic mobilization was performed using medialto-lateral dissection similar to standard laparoscopic techniques [4]. The splenic flexure was mobilized for tension-free anastomosis as necessary. After these procedures, the second and third robotic arms were undocked and moved to the third and fourth ports, respectively. Rectal mobilization was started at the level of the sacral promontory along the avascular presacral plane. Posterior dissection was performed in this plane down to the pelvic floor and the inferior hypogastric nerve was preserved. A left lateral dissection was performed, followed by a right lateral dissection. Anterior dissection was performed under Denonvilliers' fascia using Cadiere forceps in the third arm for retracting the seminal vesicle, prostate, or vagina. After complete rectal mobilization, a digital rectal examination was performed to evaluate the distal resection margin.

The robotic surgical system was then undocked and the remaining procedures were performed laparoscopically. To transect the rectum, we replaced the first 8-mm port with an 11-mm port and used one or two endoscopic linear staplers as appropriate. The specimen was extracted via a 4- to 6-cm abdominal incision across the fourth port. A double staple colorectal or a hand-sewn coloanal anastomosis was performed. Finally, a diverting loop ileostomy was created at the specimen extraction site and a pelvic drain was placed via the third port.

The chi-square tests or Fisher exact test for categorical variables and Student t test or the Mann-Whitney test for continuous variables were used to assess the statistical differences between the two groups. Values of p < 0.05 were considered statistically significant. Statistical analyses were performed using SPSS ver. 12.0 (SPSS Inc., Chicago, IL).