Performance of robot-assisted colon surgery (RCS) was first reported by Weber et al. (1). Before the introduction of RCS, laparoscopic colon surgery (LCS) was reported to be associated with reduced overall morbidity, shortened length of hospital stay, faster recovery of oral intake, and improved intestinal function compared with open surgery (2-4). The development of minimally invasive surgery has led to increased transition from LCS to RCS over the last decade in Japan. However, few reports have made a comparison between RCS with overlapping anastomoses and LCS for right-sided colon cancer. Moreover, it is unclear whether the introduction of RCS in municipal hospitals could be as safe as that in high-volume centers. Therefore, this study aimed to compare the short-term outcomes of patients who underwent RCS and LCS at a local municipal hospital in Japan.

We retrospectively evaluated consecutive patients who underwent elective laparoscopic surgery and robot-assisted surgery using the overlap method for right colon cancer at the Division of Surgery, Gastroenterological Center, Medico Shunju Shiroyama Hospital between January 2021 and July 2023. The overlap anastomotic method was introduced in our hospital for patients with early to advance stage colon cancer who undergo LCS. The study protocol was approved by the Division of Surgery, Gastroenterological Center, Medico Shunju Shiroyama Hospital, Habikino, Japan (approval number: 2018-004, and the study was performed in accordance with the Declaration of Helsinki. Standard procedures were similar for all patients and were performed by the same surgical team. Patients with double cancer or delta anastomosis were excluded. Written consent has been obtained from all patients and relevant persons (such as the parent or legal guardian) to publish the information, including photographs.

Operative procedure. We used six trocars, and the port placement is presented in Figure 1. After maintaining the intra-abdominal pressure at 10 mmHg at pneumoperitoneum, the patients were positioned in a 0-15˚ head-down position and tilted 10˚ to the left. A technique with a robotic procedure using the da Vinci^® Xi surgical system (Intuitive Surgical, Sunnyvale, CA, USA) was employed for all procedures with a retroperitoneal approach. After bowel and intestinal mobilization and lymphadenectomy, the patient was positioned at 3˚ head-up; a cranial approach was used at the hepatic curvature.

Laparoscopic colectomy (LC) or robot-assisted colectomy (RC) with overlap anastomosis. A small trocar incision was made at the umbilical port. In the case of extracorporeal anastomosis, the bowel was externalized after protecting with a wound protector. The ileum or colon was resected using 60-mm linear staples, and ileocolostomy was performed using a 60-mm linear stapler. The enterotomy was closed using verbed sutures.

In RC with overlap anastomosis, the ileum or colon was resected intracorporeally with 60-mm linear staplers, and the enterotomy was closed using the Albert–Lembert method after performing a side-to-side ileocolostomy with a 60-mm linear stapler. The specimen was then extracted through mini-laparotomy over the transumbilical port site. A drainage tube was placed after surgery.

Surveillance after surgery. Surveillance after surgery was performed in accordance with the Japanese guidelines. Briefly, the patients underwent interviews, physical examinations, tumor marker examinations, and whole-body computed tomography every six months.

Statistical analysis. Statistical analysis was performed using the EZR software (Saitama Medical Center, Jichi Medical University, Saitama, Japan). The two groups were classified as independent, unpaired groups. Data are expressed as average with mean±standard error. The statistical significance of the data was determined using the one-way analysis of variance, Fisher’s exact, chi-squared, or Student’s t-test. Statistical significance was set at p<0.05.

A total of 40 patients were analyzed. The preoperative baseline patient characteristics are shown in Table I. The operative, pathological, and oncological findings are presented in Table II. Diverting ileostomy was performed in 1 of the 40 anastomosed patients (2.5%). Only patients with thromboembolic lower-limb arterial occlusion were treated with catheter dilation therapy, and the other conditions were managed conservatively. Finally, 16 patients in the RC group and 24 patients in the LC group were compared and analyzed (Table III). Two patients in the LC group required conversion to open surgery. The operative time, bleeding, distal and proximal resection margins, length of skin incision, postoperative complications, and postoperative length of hospital stay were not significantly different between the LC and RC groups.

As a technological advance, RC has minimized enhanced camera guidance, tremors, and articulated functions within a few years in Japan, all of which have improved dissection. These methods have been improved to simplify the dissection in the deep and narrow pelvis (5-8). Short-term outcomes and benefits of RC compared with that of LC have been reported in randomized controlled trials. A systematic review and meta-analysis by Cuk et al. (9) was the first to compare robot-assisted surgery with laparoscopic surgery for colon cancer resections. That study, which included 14,093 patients and reported the short-term clinical outcomes, indicated that RCS was superior to LCS in terms of anastomotic leakage rate, overall complication rate, conversion to open surgery, and time to start a regular diet. Despite the lack of prospective studies included in the meta-analysis, these results were confirmed by supplementary statistical analyses. These results indicate that the robot-assisted method has several clinical benefits compared with laparoscopy in predominantly right-sided tumors, which may defend its standardized implementation for the future treatment of right-sided colon cancer. Our robotic approach of overlapping anastomosis results showed that RC with overlap is similar to LC with overlap. We applied the robot-assisted overlap technique in RC and compared its short-term effects with those of LC. Some researchers worry about technical difficulties and long operation times because of anastomosis (10). We began performing robot-assisted colorectal surgery in January 2023. Our Department of Surgery established seven staff surgeons during the study period. In this study, a surgeon with expertise in the laparoscopic and colorectal fields, but without experience in robotic surgery, visited another hospital where RCS was introduced to other non-expert members to evaluate its feasibility.

In the introduction of LCS, the primary difficulty was the high rate of conversion to open surgery and intraoperative complications (11-15). Several studies have reported that the introduction of robot-assisted rectal surgery (RRS) is safe and feasible at high-volume centers worldwide. Park et al. reported an overall morbidity rate of 29.3% including an anastomotic leakage rate of 9.7%, and the incidence of major complications was 9.8% in their first 41 cases of RRS (16). In colon cancer, the colonic mesentery is oncologically responsible for the vascular and lymphatic drainage of the colon, and complete mesocolic excision (CME) shares similarities with the concept and surgical technique used for total mesorectal excision in rectal cancer. Previous studies have shown that CME is oncologically beneficial (17). The reason for this was thought to be the several possible advantages of the RRS over laparoscopic rectal surgery. This is because the instruments are designed to move seven degrees of motion, which is greater than the angle of the human wrist and provide a three-dimensional surgical view and steadiness. Robot-assisted right colon resection with intracorporeal anastomosis was reported by Trastulli et al. (18) to be feasible and safe. In our study, operative time, bleeding, and complications were not significantly higher in the RC group than in the LC group. We are concerned that the reason for our short-term robotic outcomes is the standardization of port placement and technical procedures. This indicated that the robot-assisted method had some clinical benefits compared with laparoscopy for right-sided tumors, which may defend its standardized implementation for the future treatment of right-sided colonic cancer. However, that was a non-randomized retrospective study, and the overlapping series was limited; therefore, the quality of evidence in that study was low. However, our results showed that RCS was associated with several beneficial outcomes. There are a few reports on the effectiveness of overlap anastomosis in patients who underwent RCS (9). With the introduction of robotic surgery, we have performed an overlapping method for right colic cancer. In the case of laparoscopic surgery, it is sometimes difficult to use intracorporeal anastomosis because of the lack of a fitting angle of the staple. Moreover, in cases of massive tumors such as T4 and obesity, we are concerned about the use of overlap anastomosis; therefore, we performed intra- or extracorporeal anastomosis after right-sided colon mobilization and lymph node dissection. We believe that, by using different suturing devices depending on the tumor situation, it is possible to perform adequate anastomosis. With an increasing number of robots, we believe that our overlap anastomotic technique will be safe, and the introduction of RCS will be facilitated.

In conclusion, this pilot study demonstrated that RC was safe and feasible, given that surgeons had sufficient skill and experience in both LC and colorectal surgery, and were provided advice from experienced outside proctors in the initial phase.

The Authors declare that there are no conflicts of interest in relation to this study.

MI acquired data and drafted the manuscript. TN, MO, YU, MT, RK and TI drafted the manuscript. TN revised the manuscript critically. All the Authors have read and approved the final manuscript.

The Authors thank Toshikatsu Nitta, PhD, for editing a draft of the manuscript.

No external source of funding was sought for this research.