Robotic-assisted versus laparoscopic colorectal surgery: a meta-analysis of four randomized controlled trials

Minimally invasive surgery for colorectal disease was introduced in 1991 [1]. Such surgery has been widely used worldwide and has become increasingly popular. However, technical barriers, including unstable video camera imaging, loss of dexterity and a steep learning curve, preclude the widespread adoption of minimally invasive surgery techniques for colorectal disease. To overcome these technical drawbacks, robotic surgical systems were introduced. Robotic laparoscopic colorectal surgery (RCS) was first reported in 2002 [2]. Since then, many studies of RCS have been widely reported [3‐5]. RCS has some advantages over conventional laparoscopic surgery (LCS). These advantages include a three-dimensional image, convenient movements of the robotic arm, no tremor, motion scaling, a short learning curve, dexterity and ambidextrous capability [4, 6, 7]. Some studies have already proven that robotic laparoscopic colorectal surgery is associated with certain benefits compared to conventional laparoscopic colorectal surgery [8‐10]. Additionally, the learning curve for robotic surgery is short [11]. However, the relative merits of RCS versus LCS are controversial. The aim of this study was to compare the efficacy and safety of RCS and LCS via a meta-analysis of the available randomized controlled trials (RCTs).

Laparoscopic surgery has been applied in many surgical fields and has not only been shown to be effective and safe but also to have certain benefits over traditional open surgery [17‐19]. However, limitations to the performance of laparoscopic surgery remain, including the high conversion rate to open surgery [20]. The advent of robot-assisted surgery has overcome some of the limitations of laparoscopic surgery and has been successfully applied to urology, general surgery, gynecology and other surgical fields [21, 22]. Several meta-analyses have suggested that robotic laparoscopic surgery is feasible, produces similar perioperative outcomes and is oncologically safe [23, 24]. Robotic surgery may result in shorter hospital stays, reduced blood losses and lower conversion rates, but it also may require increased operation time costs [24].

A previous meta-analysis [25] produced a similar conclusion regarding the comparison of robotic laparoscopic surgery to laparoscopic surgery in colorectal disease. However, the studies that were included in this previous meta-analysis were of relatively low quality, and the number of patients was relatively small. Additionally, the benefits of robotic surgery for colorectal disease remain controversial. Thus, we conducted this meta-analysis based on four RCTs to draw a clearer conclusion.

The present study is the first meta-analysis to compare robot-assisted and laparoscopic surgery for colorectal cancer based only on RCTs. The results of this meta-analysis revealed that RCS may provide additional benefits over LCS and that it is safe and effective [3, 4, 26]. Regarding operation times, RCS exhibited a tendency to take longer than LCS, but this difference was not significant (P = 0.06). This result is similar to that of a previous study [27]. In contrast to this view, other studies have reported that RCS requires more time than does LCS [28, 29]. As the surgeons’ robotic experience increases and the techniques are improved, the operation times will be reduced [26]. However, in this regard, obvious heterogeneity existed among the studies; the reasons for this heterogeneity were as follows. First, the surgeries were performed by different surgeons who were not at the same point on the learning curve and had different amounts of experience. Additionally, the RCS group of one study contained a large number of patients who had previously undergone abdominal surgery [14], and it is well-known that previous surgery inevitably increases the difficulty of performing surgery.

EBL ranges between 90 ml and 320 ml for LCS [30] and between 20 ml and 486 ml for RCS according to a recently published review [31]. Our studies showed that the average EBL was 81.83 ml for RCS and 92.88 ml for LCS. Both studies reported no significant difference between the two groups in this regard. However, the pooled data revealed that the EBL was significantly lower for the RCS group than for the LCS group. This finding is consistent with those of previous studies [31]. However, the surgery that was performed by skilled surgical teams exhibited similarly low levels of EBL for the two techniques [4]. Due to lower EBL, it is possible to suggest that RCS may significantly reduce the probability of transfusion and might prevent the recurrence of cancer. A review reported that patients who receive more perioperative transfused blood are at greater risk for cancer recurrence and that this risk is independent of tumor stage at surgery [32]. It is well-known that the prognosis for colorectal cancer after surgery is highly dependent on the cancer stage at surgery. However, the EBL during colorectal cancer surgery influences long-term survival according to a previous study [33]. Massive blood loss during colorectal cancer surgery is probably related to advanced disease or the recurrence of cancer [34], preoperative therapy (neoadjuvant therapy with either chemoradiation or chemotherapy alone), unclear anatomy [35] and the lack of experience of the surgical team rather than the type of surgical approach. Because only two studies reported EBL in this analysis, further studies are necessary to prove whether RCS results in lower blood loss.

We found that the conversion rate was significantly lower in the RCS group and there was no significant heterogeneity across the four studies. Thus, the reduction in conversion rate may be one of the key benefits of RCS. Conversion rate is a valuable index of surgical quality. Lower conversion rates are associated with fewer postoperative complications [20]. The reduction in conversion rate may be attributable to the fact that robotic surgery can facilitate certain steps in colorectal procedures. These procedures include splenic flexure takedown, dissection of the inferior mesenteric vessels, dissection in the narrow pelvis [36], et cetera.

As observed in the studies, robotic surgery has other advantages. The time to the recovery of bowel function was shorter in the RCS than in the LCS group. This reduction may be another potential benefit of RCS because faster returns to normal diets are associated with faster recoveries. We discovered that the LOS was not significantly different between the two groups; indeed, LOS was similar between the two techniques [26]. The complication rates of the patients who underwent RCS and LCS were similar. This finding also demonstrates that RCS is as safe and feasible as LCS [37]. Regarding the pathological details, there were no differences between the two techniques in terms of proximal margins, distal margins or harvested lymph nodes.

Although we conducted this meta-analysis based on four RCTs, this meta-analysis still has the following limitations. First, the included studies were not double-blind studies or even single-blind studies; the studies may have been biased; therefore, the interpretation of their results may also have been biased. Second, although we focused on colorectal surgery, different types of diseases (for example, rectal cancer, sigmoid colon cancer, right colon cancer) that involved different types of surgery were included, which may have caused heterogeneity. Third, the surgery in the included cases were not performed by the same surgeon, and the experience and technique of the surgeons may have affected some of the indices, such as the operation time, EBL and conversion rate. However, in this meta-analysis, no significant heterogeneities among the four studies were found for conversion rate or EBL; only operation time exhibited significant heterogeneity. Fourth, long-term follow-up evaluations assessing oncologic outcomes were not available from the selected studies, and only Patriti et al. [14] reported medium-term outcomes. Fifth, the available included RCT studies were limited, and the numbers of operations were small; however, other RCT studies comparing RCS and LCS, such as the ACOSOG Z6051 and ROLARR studies, are ongoing [38]. Finally, only one study compared costs between RCS and LCS [13]. This study revealed that the overall hospital costs were significantly higher for RCS than for LCS. Robotics is a new trend in colorectal surgery, and more attention has been paid to the high cost that is associated with this new technique. A variety of studies have reported that the cost of robotic colorectal surgery is higher than that of laparoscopic surgery [3, 39, 40]. The high capital and running costs of robotic systems have precluded their widespread use in many countries [41]. Furthermore, one study reported that RCS does not provide sufficient advantages over LCS but significantly increases the total cost [38]. Future studies should assess the cost-effectiveness of RCS based on long-term oncologic outcomes and functional results.

This meta-analysis suggests that RCS is safe and effective and has some advantages over LCS. These benefits include a reduced conversion rate, reduced blood loss and reduced time to recovery of bowel function. Regarding the other variables, such as operation time, complication rate and LOS, there were no significant differences between the two groups. However, RCS was associated with a significant increase in total costs relative to LCS. Further well-designed, prospective controlled randomized trials should be conducted to assess the financial benefits and the long-term oncologic outcomes of RCS.