Bowel dysfunction, which occurs in many patients after rectal surgery, includes fecal incontinence, urgency, and frequent bowel movements. The LARS score has been developed as a method of evaluation for bowel dysfunction and has been translated and validated in many languages [21, 24]. In addition, function-preserving TME for lower rectal cancer is a major factor that induces fecal incontinence . It is known that fecal incontinence is associated with a unique decrease in QOL, so the fecal incontinence quality of life score (FIQL) questionnaire and the modified FIQL have been developed as evaluation methods of this phenomenon [22, 26]. On the basis of these results, it was clarified that the factors inducing bowel dysfunction after function-preserving rectal resection were low anastomosis and preoperative radiotherapy [27–29]. The modified FIQL has also been used to demonstrate the functional validity of intersphincteric rectal resection .
This simple assessment of function has made it possible to compare new treatment strategies and is now one of the indicators for clarifying the usefulness of laparoscopic surgery in preserving function. In this study, all patients that underwent conventional laparoscopic surgery and taTME had major LARS; however, with robotic surgery, 1 in 5 patients avoided major LARS. And the number of patients with permanent stoma was significantly reduced in robotic surgery compared to taTME. One of the reasons for this may be the reduction in short-term postoperative complications, especially anastomotic leakage, which is supported by recent reports that robotic surgery contributes to a reduction in short-term complications compared with conventional laparoscopy . In addition, a stable field of view and delicate dissection in the deep pelvis were achieved in the robotic modality, which may have contributed to the preservation of fine sphincter nerves such as the internal anal sphincter nerve and the levator ani nerve [32, 33]. In addition, anterior dissection in the anal canal can be performed more easily using a robot than conventional laparoscopy, and this may reduce damage to sphincter muscles which was also estimated to occurred in taTME because of the use of transanal platform and the longer time to manipulate the anus.
LLND or preoperative radiation therapy may be added to standard TME to improve local control of locally advanced lower rectal cancer [34, 35]. In Japan, LLND has been described as a standard treatment strategy for locally advanced lower rectal cancer in the official guidelines . In recent years, the necessity of LLND has been pointed out in selected cases even in Europe and the United States . A study with a small number of cases reported that LLND has an adverse effect on bowel function . In this study, LLND had no influence on bowel function in the robotic group. On the other hand, preoperative radiotherapy is known to be a clear factor in bowel dysfunction . Under such circumstances, several clinical trials on preoperative chemotherapy are being conducted in anticipation of reaping the dual effects of improving oncological control when substituted for radiotherapy and avoiding bowel dysfunction caused by radiotherapy [40, 41]. In recent years, preoperative chemotherapy has been shown to be as effective as preoperative chemoradiation in local control and reducing bowel dysfunction, suggesting that it is a useful treatment strategy . At our institution, preoperative chemotherapy for locally advanced rectal cancer has been conducted as part of a clinical study . However, even with the strategy of avoiding radiation, the rate of bowel dysfunction after TME, especially after hand-sewn anastomosis, was shown to be extremely high in this study, so new treatment strategies should be developed. Currently, the results of the watch-and-wait strategy (WW) have been reported in patients with complete response after chemoradiotherapy, and its oncological safety and efficacy have been clarified . In addition, WW was shown to be more effective than function-preserving rectal resection after chemoradiotherapy in terms of bowel function . However, in this report, it was found that chemoradiotherapy itself may also cause bowel dysfunction, and it is unclear whether TME alone or chemoradiotherapy alone is more harmful to bowel function. In recent years, WW has been shown to be associated with milder bowel dysfunction than TME alone . However, because it was a retrospective study, its interpretation is controversial due to the heterogeneity of the observation period and surgical approach. In particular, prospective comparative studies between WW and robotic DST anastomosis which is suggested to be useful in this study are warranted.
In terms of urinary function, it has been reported that robotic surgery is more effective than conventional laparoscopic surgery at both 6 and 12 months postoperatively [14–16]. Also in this study, robotic surgery has been shown to be more effective in preserving urinary function than conventional laparoscopic surgery. On the other hand, postoperative urinary function was comparable between taTME and robotic surgery. Compared with conventional laparoscopic surgery, taTME was also reported to be effective in preserving urinary function, and the results of this study support this . In consideration of the preservation of both bowel and urinary functions, the results of this study suggest that robotic surgery may be a better approach for function-preserving TME.
There were several limitations to this study. Although this was a prospective observational study, it is possible that robotic surgery had better results reflecting experience with conventional laparoscopy and taTME. The taTME group differed from the conventional laparoscopic group with regard to the fact that the results were obtained from the very first case, which may have resulted in poor results due to the initial learning curve. In addition, since all anastomoses in the taTME group were hand-sewn in the anal canal, the results may have been different had a mechanical anastomosis been performed above the anal canal. Laparoscopic surgery was performed by a single surgeon, and the results may differ had they been obtained from multiple surgeons, thus the study is lacking some external validity. Despite the existence of these limitations, we believe that one of the advantages of robotic surgery is that good results can be expected from the introduction of robotic surgery in the early stages of use, because these results are from the earliest cases of robotic surgery at the institution and from two different surgeons.