Transanal Total Mesorectal Excision in Lower Rectal Cancer: Comparison of Short-Term Outcomes with Conventional Laparoscopic Total Mesorectal Excision

Introduction

Since the description of total mesorectal excision (TME) by Heald and Ryall,^1,2 TME has been a standard surgical principle for the treatment of rectal cancer. ³ However, a narrow pelvic cavity, male patients, or obesity increases the difficulty in performing TME and maintaining an uninvolved circumferential margin (CRM) or safe distance of distal margin. ⁴ The laparoscopic surgery in the past two decades has gradually replaced open surgery, especially in colon cancer, primarily because of reduction in surgical trauma, a shorter hospital stay, and a faster recovery without poor oncological outcomes compared to those with open surgery. ⁵ However, in the case of rectal cancer, two prospective randomized studies on laparoscopic and open surgeries demonstrated that laparoscopic surgery did not result in noninferiority compared to that with open surgery in terms of pathological outcomes.^6,7 In the COLOR II trial, the largest randomized prospective study on open and laparoscopic surgeries, 17% of patients were converted to open surgery due to narrow pelvic cavity, even though the patients undergoing laparoscopic surgery had faster recovery and the same oncological results compared to those of open surgery. ⁸

Transanal total mesorectal excision (TaTME) was first introduced by Lacy in 2011. ⁹ This approach provided better specimen quality and more completeness of TME than those with the tram-abdominal approach using a single-port platform.^10–13 The advantage of TaTME includes dissecting and transecting the rectum from the lower edge of the tumor by direct vision, so that a safe distal margin and mesorectal excision can certainly be confirmed at the initial stage of dissection. ¹⁴ Therefore, the lower the location of the tumor is, the more benefits can be reflected by TaTME. We present our initial results of short-term outcomes with TaTME in comparison with laparoscopic TME (LaTME) in the treatment of lower rectal cancer.

Methods

Results

Twenty-three consecutive patients with lower rectal cancer who underwent TaTME were included in this study. Another 23 patients with lower rectal cancer treated by laparoscopic surgery matched for age, gender, ASA score, and clinical TNM staging were also analyzed. The characteristics of these patients are shown in Table 1. There were no statistically significant differences between both groups in terms of age, sex, ASA score, BMI, tumor location from the anal verge, clinical TNM staging, and preoperative neoadjuvant chemoradiotherapy.

The characteristics of surgery in both groups are shown in Table 2. All patients in the LaTME group received laparoscopic low anterior resection and anastomosis by stapling, and 1 of 23 patients in the TaTME group received intersphincter dissection and coloanal anastomosis. In both groups, there were no differences in terms of the duration of operation, blood loss, postoperative hospital stay, and protective stoma rate. There was no conversion in either the LaTME or TaTME group. One patient had anastomotic leakage in the TaTME group, and 1 patient had stroke 5 days after the operation in the LaTME group. One patient in each two groups had postoperative ileus and had smooth recovery after supportive treatment. No perioperative mortality was observed in both groups.

Table 3 shows the pathological characteristics of both surgical groups. There were no significant differences in terms of tumor size, pathological TNM staging, distal margin of specimen, and harvested lymph nodes. The only difference was the involvement of CRM. There were 4 patients in the LaTME group with CRM <1 mm compared to no patients in the TaTME group with CRM <1 mm.

Discussion

Our study showed that TaTME is a safe and effective treatment, and there were no significant differences between LaTME and TaTME in terms of the duration of operation, amount of bleeding, and intraoperative or postoperative complications. TaTME involves a longer duration of surgery than that of LaTME, because of two steps of procedure that cannot be performed simultaneously, ¹⁵ and two teams will increase the speed of surgery, and the operation duration will be shorter than that of LaTME. ¹⁶ Although we performed a one-team operation, the duration of operation in the two groups was not significantly different. This may be because it took a long time for dissection in all patients with lower rectal cancer in the LaTME group.

The difficulty of laparoscopic surgery in lower rectal cancer was relatively higher than that for upper and middle rectal cancer to achieve completeness of TME and uninvolved CRM because of the limitation of laparoscopic vision in the narrow pelvis, especially in patients with obesity, shorter distance of tumor from the anal verge, and a narrow pelvis.^4,17 In TaTME, the initial dissection from the lower edge of the tumor is very close to the anus, which made it easy to confirm the safety of the distal margin and CRM. Air insufflation will accelerate the avascular plane dissection at the pelvic posterior and anterior walls when a full-thickness transection of rectum is performed. The relatively long distance in the upper and middle rectum makes it difficult to perform purse-string suture and initial dissection. The long distance from the anus sometimes makes the surgeon to sacrifice the too long healthy rectum in upper or middle rectal cancer; otherwise, it is effective to perform laparoscopic surgery to treat upper rectal cancer. Therefore, our study analyzed only patients with lower rectal cancer (≤7 cm from the anal verge) to evaluate the treatment results of TaTME and LaTME.

TME has been shown to decrease the local recurrence rate from 20%–45% to 10%. ¹⁸ The involvement of CRM is also an important factor for increasing the local recurrence from 12.7% to 37.6% when the CRM is <1 mm. ¹⁹ Although laparoscopic surgery had better vision in the narrow pelvis than that with traditional open surgery, the CRM involvement rates in the COLOR II study were still 9% and 10% in middle and lower rectal cancer. ⁸ In our study, all patients in the TaTME group had a CRM of ≥1 mm, and there were 4 patients with CRM <1 mm in the LaTME group. We believe that down-to-up dissection from the anus in TaTME made the surgeon perform a more accurate avascular plane dissection in the pelvis.

Majority of recent studies have shown that TaTME has a high rate of uninvolvement or longer distal margin compared to that with LaTME,^{10,16,20–22} but there was no significant difference in our study between the two groups. There were 14 patients with tumor location ≤4 cm from the anal verge in the TaTME group, and hence, there was no space to achieve a relatively long distal margin. Meanwhile, there was 1 patient with distal margin involvement in the LaTME group, but there were no patients in the TaTME group with such situation.

Since TaTME is performed in the intrabowel lumen, there is a risk of iatrogenic perforation of the rectum and possible bacterial contamination that could potentially cause intra-abdominal abscess or anastomotic leakage. In the study by Velthuis et al., 39% of the patients developed positive cultures 17% of them developed a pelvic abscess after the operation. ²³ However, no patient in the two groups developed pelvic abscess in our study, and only 1 patient had anastomotic leakage.

Some limitations exist in our study. First, patients in the LaTME group were operated by 2 surgeons, whereas those in the TaTME group underwent the operation by a single surgeon. Second, there were no postoperative functional results between the two groups. Finally, it is not a randomized controlled study, and thus we cannot definitely rule out a potential bias.

Conclusion

TaTME is a novel technique for the treatment of rectal cancer, and our short-term analysis showed that it is a feasible and safe procedure for the treatment of lower rectal cancer. TaTME had better pathological outcomes with CRM uninvolvement compared to those with laparoscopic surgery. A randomized controlled trial for functional results and long-term oncological results is necessary for further evaluation.