Comparison of perioperative and short-term outcomes between robotic and conventional laparoscopic surgery for colonic cancer: a systematic review and meta-analysis

In the last decade, laparoscopic surgery has become popular in many surgical fields due to its advantages compared to the open approach, such as less pain, faster recovery/resumption of daily activities, and better cosmesis [1, 2]. However, because laparoscopic surgery is more technically demanding, for reasons including the limited range of instrument motion, relative loss of dexterity, and inadequate visualization, laparoscopic surgery continues to be stressful for surgeons, and the learning curve is very steep [3, 4]. The da Vinci robotic surgical system (Intuitive Surgical, Sunnyvale, CA, USA) has been applied to overcome the ergonomic discomfort of laparoscopic surgery, with advanced technologies including superior 3-dimensional views and an internal articulated EndoWrist® that improves dexterity and allows seven degrees of freedom [5, 6]. With these advantages, robotic surgery (RS) has been adopted rapidly for advanced surgical procedures in many fields, such as urologic, gynecologic, and cardiac surgery [7, 8, 9].

The first robot-assisted colorectal surgery was reported in 2002 [10]. Recently, much of the reported data has been from robotic surgeries for rectal cancer, because robotic technology is of maximal advantage in narrow spaces such as the mediastinum and pelvic cavity, and it is very useful for the pelvic dissection known as total mesorectal excision in rectal cancer surgery [11, 12]. On the other hand, the role of robotic surgical systems in colonic surgery is still under debate. Thus, there are a few reports of robot-assisted colonic surgery, and only one meta-analysis of RS for right colon cancer has been reported [13]. Therefore, we conducted a systematic review of the available evidence comparing the surgical safety and efficacy of RS with that of conventional laparoscopic surgery (CLS) for colonic cancer.

Our study showed that robot-assisted colectomy was feasible and safe compared with CLS in terms of intraoperative and postoperative complications and the rate of open conversion. In addition, the times to diet resumption, recovery of bowel function, and postoperative hospital release were shorter in the RS group than in the CLS group. In the RS group, the EBL was lower and the proximal margin of the specimen was longer, but the operative time was significantly longer than in the CLS group. These results are similar to those of other published studies and the previous meta-analysis for rectal cancer [12, 23, 24, 25].

To date, most of the published data for robotic colorectal surgery have described rectal cancer surgery, because the advantages of robotic technology are maximized in narrow spaces such as the pelvic cavity, and robotic systems have been adopted more rapidly for rectal surgery than for colonic surgery [11, 26]. Most of the studies comparing robotic rectal surgery with conventional laparoscopic rectal surgery have reported good results for RS in terms of safety outcomes, and comparable or better results in terms of efficacy outcomes, except for operation time. The current study demonstrated that the advantages of robotic systems shown in rectal surgery also hold true in colonic surgery. To date, there has been only one systematic review comparing robotic and laparoscopic surgeries for right colectomy, which was reported by Xu et al. [13]. Otherwise, our study is the first systematic review including whole colonic surgery from the right colon to the sigmoid colon.

In fact, colonic surgery can be divided largely into right-sided colectomy and left-sided colectomy, and the 2 types of surgery are very different. There are differences between the 2 groups in most fields of anatomy, tumor characteristics, methods of dissection and anastomosis, and these can affect the incidence of complications and the prognosis. Therefore, the advantages of robotic systems may differ in right-sided colectomy and left-sided colectomy generally. In conventional laparoscopic right-sided colectomy, extracorporeal stapled anastomosis is commonly performed through minilaparotomy. Robotic technology in right-sided colectomy facilitates intracorporeal hand-sewn anastomosis, and can reduce the incision size for specimen extraction, shift the incision site to a Pfannenstiel incision, cause less pain, less incisional hernia and allow better cosmesis [20, 27, 28]. On the other hand, the advantages of robotic left-side colectomy can be expected to be similar to those of robotic rectal surgery, such as nerve preservation during inferior mesenteric artery dissection, and easy mobilization of the splenic flexure [29].

Because the expected advantages of robotic technology differ among surgery types, the fact that this study included whole colectomy may be a limitation. Nevertheless, it may be an important and significant finding of this study that the advantage of robotic rectal surgery can be applied equally for colonic surgery. In our study, robotic colectomy was not only feasible, but also safe compared with CLS. However, the operative time was significantly longer in the RS group, as reported in other studies, because additional time may be necessary for robot set-up, docking, and the learning curve [30].

A very interesting observation in our study was that there was no difference in the conversion rates of robotic and laparoscopic colectomy. Xu et al. [13] reported similar results. In previous reports of rectal surgery, however, the conversion rate usually was lower in the RS group than in the CLS group [23, 24, 25], because the robotic system may help to overcome the anatomical difficulty of the narrow pelvis; this point has been important in justifying the use of robotic rectal surgery. On the contrary, the level of difficulty of colectomy is easy compared with proctectomy, so this advantage of RS may not appear significant for colectomy, although there are some merits of RS for intracorporeal suture or splenic flexure mobilization. Thus, there might not be a significant difference in the conversion rates of the two procedures. This has been the weak point in the justification of the very high cost of RS compared with laparoscopic surgery for colectomy, unlike for rectal surgery, and remains a controversial topic. As our study also demonstrated, however, there are many advantages of RS, such as lower blood loss, earlier recovery of bowel function, shorter hospital stays, and longer proximal margins of the specimens, and future studies should be performed to evaluate more potential advantages of robotics.

Despite our findings, this study has several limitations. First, there were limitations in the meta-analysis because of the lack of primary studies comparing RS and CLS for patients with colonic cancer. There is a need for additional high-quality primary studies, and when a sufficient number of primary studies become available for analysis, another systematic review and meta-analysis should be conducted and compared with this study. Second, in the present study, three out of 6 studies were conducted among Koreans living in South Korea. The regional concentration of a study population commonly influences the generalizability and makes it difficult to interpret the results in the context of other countries. Finally, the comparability of the studies included in the meta-analysis was weak due to differences in baseline attributes between patients who underwent RS and CLS in the cohorts. In 2 of the 6 studies, patients who received RS were younger than those who received CLS, and the tumor sizes differed between patients who had received RS and CLS.

Prospective, protocoled long-term follow-up studies that report the oncologic results of both CLS and RS are needed to evaluate the safety and efficacy of RS. Moreover, this technique for patients with colonic cancer is still in its infancy, and thus, the technique must be reassessed once the learning curve has been overcome.

In conclusion, the present study found the times to resumption of a regular diet, first passage of flatus and defecation were shorter for RS than for CLS. Also, RS was associated with a shorter hospital stay, lower EBL and longer proximal margin than CLS. However, RS was associated with a longer surgery time. For a more accurate understanding of RS for colonic cancer patients, robust comparative studies and randomized clinical trials including a sizeable number of subjects that take into account future actions are required.