Comparison of the perioperative outcomes of laparoscopic surgery, robotic surgery, open surgery, and transanal total mesorectal excision for rectal cancer: An overview of systematic reviews

Abstract Regarding the surgical approaches for rectal cancer, many techniques have been reported in randomized controlled trials, meta‐analyses, and reviews of comparisons between two techniques, e.g. open surgery vs laparoscopic surgery, laparoscopic surgery vs robotic surgery, or laparoscopic surgery vs transanal total mesorectal excision. Since robotic surgery and transanal total mesorectal excision were developed after laparoscopic surgery had become an established minimally invasive technique, they have each been compared with laparoscopic surgery. Therefore, a review was performed to compare the surgical outcomes of robotic surgery and transanal total mesorectal excision, and to perform such comparisons among ≥3 of the above mentioned approaches, in the expectation that this review will serve as a reference for aiding treatment selection in future. The results of the current review suggest that all of the examined procedures have advantages and disadvantages, but that there are no decisive factors that could be used to select one procedure over any other. At the present time it cannot be demonstrated that laparoscopic surgery, robotic surgery, transanal total mesorectal excision, or open surgery is superior to the other techniques, and it is important to select the best technique for each patient from among those that a surgeon can perform. It is also important to maintain a flexible attitude that allows new techniques to be adopted as needed in the future.


| INTRODUC TI ON
Although open surgery (OpS) has conventionally been performed as the only form of radical surgery for rectal cancer, laparoscopic surgery (LaS) is widely indicated for rectal cancer as a minimally invasive surgery. The therapeutic outcomes of these procedures have been compared in several randomized controlled trials (RCTs) and meta-analyses, which confirmed that there were no significant differences in long-term prognosis. [1][2][3][4][5][6][7][8] In 2017, it was reported that the quality of LaS was significantly lower than that of OpS, and thus, concerns about the safety of LaS could not be refuted. [9][10][11][12] However, no data suggesting that the long-term prognosis of LaS is worse than that of OpS were obtained in these clinical studies, and at present the safety of LaS is widely accepted when it is performed by a sufficiently experienced laparoscopic surgical team. [13][14][15] On the other hand, the first robotic surgery (RoS) for rectal cancer was reported in 2006, and the frequency of RoS for rectal cancer has been increasing due to technical advances and the accumulation of experience among surgeons. 12,[16][17][18][19] In addition, the indications for and frequency of transanal total mesorectal excision (TaTME) have also been increasing, demonstrating its efficacy. [20][21][22][23][24][25] Important information regarding TaTME has been continuously reported from the international TaTME registry. [23][24][25] However, concerns regarding its long-term oncological outcomes are still reported, and TaTME remains a developing technique which should be performed with care. 12,26,27 Recently, robotic TaTME, in which a robotic approach is used for the laparoscopic abdominal portion of TaTME, and the robotic transanal approach have been reported. [28][29][30][31][32] At present, technologies continue to advance, and surgeons select the best approach from among the surgical techniques that they can perform based on their deep understanding of the merits and limitations of each approach.
Advances in surgical technology make it necessary to examine the efficacy of new technologies, and it is essential to examine the safety and efficacy of surgery for cancer, in addition to its long-term prognosis. Regarding the four surgical approaches for rectal cancer, many comparisons between two techniques, e.g. OpS vs LaS, LaS vs RoS, and LaS vs TaTME, have been reported in RCTs, meta-analyses, and reviews. [33][34][35][36][37][38][39][40][41] These comparisons were performed between LaS and other approaches because LaS was the first type of minimally invasive surgery and was initially compared with conventional OpS, followed by RoS and TaTME, which were subsequently developed as different types of minimally invasive surgery. On the other hand, in actual clinical practice, few medical institutions or surgeons perform all four approaches, or even three of the approaches, on a routine basis, and thus it is difficult to conduct an RCT that compares three or four of the approaches at once. This review was conducted to compare the surgical outcomes of RoS and TaTME, and to perform such comparisons among three or more approaches, in the expectation that it will serve as a reference for aiding treatment selection in the future. We reviewed studies that were published since 2018 in order to consider the latest findings.

| ROBOTI C SURG ERY VS TR AN SANAL TOTAL ME SOREC TAL E XCIS ION
Since RoS and TaTME were developed after LaS had become established as a minimally invasive technique, RoS and TaTME have each been compared with LaS. In addition, since these techniques are indicated for the same patients, few medical institutions perform both RoS and TaTME. Thus, it is rare for RoS and TaTME to ever be compared directly.
Recently, some studies involving direct comparisons between RoS and TaTME have been published (Table 1). Perez et al 42 compared the intraoperative and perioperative outcomes of 60 and 55 cases in which RoS and TaTME, respectively, were performed for low or middle third rectal cancer using data from a prospective database.
In this study, all of the robotic surgical procedures were performed at one institution, and all TaTME procedures were conducted at another institution. The operating time and perioperative complications rates did not differ between the groups, and the circumferential resection margin (CRM) was wider in the RoS group than in the TaTME group, while none of the remaining oncological parameters exhibited intergroup differences. Therefore, it was concluded that both procedures should be considered equally feasible for low rectal cancer and as alternatives to conventional anterior resection (open or laparoscopic).
Law et al 43 compared the intraoperative and perioperative outcomes of 80 cases of sphincter-saving RoS and 40 cases of TaTME for rectal cancer by analyzing a prospective mono-institutional database using propensity score matching. Some significant differences between baseline characteristics were observed including with regard to the level of the tumor from anal verge, and, after the matching procedure, the number of abdominal incisions and the size of the tumor were the only baseline characteristics that exhibited significant differences. The operating time was significantly shorter and the amount of intraoperative blood loss was lower in the TaTME group. Thus, they concluded that both RoS and TaTME can achieve favorable rectal cancer resection outcomes and that TaTME is associated with a shorter operating time, less intraoperative blood loss, and a higher rate of transanal specimen extraction.
Gachabayov et al 44 compared histopathological metrics and/ or complication rates between TaTME and RoS for lower, middle, or upper rectal cancer. They performed a systematic search and included six observational studies involving 1572 patients (TaTME: 811; robotic TME: 761) in their meta-analysis. The CRM involvement rate, distal resection margin (mm), and complications rates did not differ between the procedures, and they concluded that compared with RoS performing TaTME for rectal cancer does not improve histopathological metrics or complication rates. Although RoS and TaTME have various merits and demerits, both procedures can produce favorable intraoperative and perioperative rectal cancer resection outcomes when performed by a specialist.

| OPEN SURG ERY VS L APAROSCOPIC SURG ERY VS ROBOTI C SURG ERY
Since 2018, two studies comparing OpS, LaS, and RoS have been published, which used different analytical methods (

| OPEN SURG ERY VS L APAROSCOPIC SURG ERY VS TR AN SANAL TOTAL ME SOREC TAL E XCIS ION
Since 2018, two studies in which OpS, LaS, and TaTME were compared at single institutions have been published (Table 3).
Perdawood et al 47 conducted a case-matched study, based on data from a prospectively maintained database of lower, middle, or upper rectal cancer patients who underwent TaTME, and a retrospective chart review of patients who underwent laparoscopic TME (LaTME) or open TME (OpTME) prior to the period covered by the database. The baseline characteristics of the three groups were comparable, and TaTME resulted in lower rates of incomplete TME specimens than LaTME, but not OpTME, and the other pathological results of TaTME were not significantly superior to those of LaTME or OpTME. On the other hand, while TaTME resulted in shorter operation times, less intraoperative blood loss, and shorter hospital stays, the complications and mortality rates of the three groups were comparable.
Chen et al 48  however, this can be explained by the fact that only one team performed TaTME. TaTME achieved better pathological results and disease-free survival than OpS, but was not significantly superior to LaS. They also reported that there were no patients with CRMs of <1 mm in the TaTME group, whereas the equivalent frequencies for the LaS and OpS groups were 7.8% and 13.0%, respectively (P = .035). Moreover, the patients in the TaTME and LaS groups also significantly exhibited better disease-free survival than those in the OpS group (P < .01).

TA B L E 2 Open surgery vs laparoscopic surgery vs robotic surgery
Both studies were retrospective and single-institutional, and further studies are needed to evaluate the short-term surgical outcomes and long-term oncological results of these approaches.

| OPEN SURG ERY VS L APAROSCOPIC SURG ERY VS ROBOTI C SURG ERY VS TR ANSANAL TOTAL ME SOREC TAL E XCIS ION
Comparisons of OpS, LaS, RoS, and TaTME have been performed using several methods ( Table 4).
The 2017 European Society of Coloproctology (ESCP) collaborating group conducted a prospective, observational, multicenter study in accordance with a pre-specified protocol, which included lower, middle, or upper rectal cancer patients who were scheduled to undergo elective total mesorectal excision for malignancy via any surgical approach. 49 Interestingly, they included patients that were scheduled to undergo RoS in the abdominal region and the TaTME approach in the transanal region. Overall, 9.0% of patients suffered anastomotic leakage. In the univariate analyses, both TaTME and robotic TaTME (P = .02) were found to be associated with a higher risk of anastomotic leakage than LaS. However, this association was lost after controlling for patient and disease factors, while strong associations with low rectal anastomosis and male sex remained. The positive CRM rate varied between the operative approaches: LaS: 3.2%, TaTME: 3.8%, OpS: 4.7%, RoS: 1%. They concluded that the TaTME approach is widely performed and is associated with acceptable surgical and pathological results. RoS, TaTME, and LaS produced similar outcomes with respect to macroscopic mesorectal excision, lymph node harvesting, and radial margin involvement, which were reflected by comparable local and LaS, although potential selection bias cannot be excluded. They concluded that all three surgical techniques were comparable in terms of TME quality and oncological outcomes and considered that good outcomes were achieved by individual surgeons selecting appropriate approaches based on their expertise. Abbreviations: NA, not applicable; TaTME, transanal total mesorectal excisionTME, total mesorectal excision.

| D ISCUSS I ON
as needed in the future; however, it is also acceptable to only start learning a new procedure after its technical and oncological safety have been established since LaS, RoS, and TaTME each have specific advantages and disadvantages, and evaluations of these procedures are currently ongoing.

D I SCLOS U R E
Funding Information: Declaration of prior publication.
Conflict of Interest: The authors declare that they have no conflicts of interest.