This study found that laparoscopic-assisted Ta-TME had great advantages over total laparoscopic and open transabdominal TME insphincter preservation, especially for patients with difficult operative conditions, such as bulky distal rectal carcinomas in male patients with a narrow pelvis or a high BMI who were treated with neoadjuvant chemoradiation therapy.
In the Ta-TME group, intraoperative sphincter preservation was achieved in 100% of the 20 patients, in contrast to rates of sphincter preservation of only 30% and 45% of patients in the transabdominal TME laparoscopy and open surgery groups, respectively. Because one patient in the Ta-TME group required a permanent colostomy after developing an anastomotic leak, the ultimate rate of sphincter preservation was 95% to date. Nevertheless, the long-term rate of sphincter preservation was much greater with the Ta-TME approach than the other approaches. Transabdominal resection of the distal rectum, either open or laparoscopic, usually uses the double-stapler technique, which necessitates the ability to transect the distal rectum with the stapler. Unfortunately, this manoeuvre is difficult or even impossible with current surgical instruments when the pelvis is deep and narrow. In addition, anastomosis may be impossible under direct visualization. Most importantly, for patients with difficult pelvis conditions, the so-called distal margin is generally overestimated, and squeezing the tumour tissue during exposure is inevitable. Such operations do not conform to the principle of no tumour. Rouanet et al. reported on 30 men with advanced or recurrent low rectal tumours associated with unfavourable anatomic or tumour characteristics who underwent a sphincter-sparing, transanal endoscopic proctectomy. Though the operated group included recurrent rectal cancer, 78% still had sphincter preservation at a median follow-up of 21 months. Local anatomy (deep narrow pelvis, fatty mesorectum), male sex, high BMI, and certain features of the tumour (anterior location and large tumours) are independent risk factors for conversion, operation time, morbidity, and noncurative resection. By overcoming existing restrictions, Ta-TME may make sphincter-preservation surgery both easier and more successful. Factors such as a narrow male pelvis and a high BMI may lead to an inevitable permanent colostomy after the conversion from laparoscopic to open surgery.
Although Ta-TME is technically feasible, the quality of surgical specimens—especially whether a complete excision of the mesorectum can be obtained and whether it might pose additional risks of local recurrence—has been questioned[19,20]. A positive CRM and its integrity are important factors in local recurrence . Available data have shown that negative CRMs were present in 87.9–97.0% of open resections and 90.5–97.1% of laparoscopic resections [22,23]. Buchs et al. reported that traditional surgical approaches may lead to a greater rate of positive CRMs for tumours less than 3 cm from the dentate line . In a study of 186 patients, Lacy found positive CRMs present in 8.1% of patients . Theoretically, a more meticulous dissection as allowed because of better visualization by the Ta-TME approach may be very helpful for achieving a negative CRM for these distal rectal tumours; indeed, this was verified by Denost et al. in a randomized clinical trial . That trial enrolled 100 patients between 2008 and 2012 with distal rectal cancers (<6 cm from the anal verge) otherwise suitable for sphincter preservation. The primary endpoint was the quality of the resection (rate of a positive CRM, the grade of the integrity of the TME, and the ability to remove the local lymph nodes). The rate of positive CRM decreased markedly after transperineal dissection compared to transabdominal distal rectal dissection (4% versus 18%; p=0.025). In our cohort, all patients in the Ta-TME group achieved a negative CRM and complete specimens. Our ability to accomplish this success rate was unexpected because it was the first cohort of patients in whom we had performed this operation, and it might be attributable to either our prior extensive experience with dissection of distal rectal tumours or to the small sample size.
Safety is important for patients and surgeons when a new technique is introduced, especially during the period of the learning curve. This technique has drawn much attention, and various training courses have been introduced in Europe and the United States. In the study by Atallah and colleagues, the mean blood loss for 20 patients was 153 mL . In a registry study of 720 cases, 61.2% of patients had blood loss of less than 100 mL, and only 1% of these patients had a blood loss of greater than 1 L. Complications, such as ureteral injury or massive haemorrhage, are among the unique complications that could be countered during this kind of surgery. The need for a non-planned re-operation, a grade III complication, indicates a serious complication. Burke et al. reported an operation rate of 12% among the first 50 patients, mainly due to ileostomy dysfunction, anastomotic leakage, or pelvic collection . In a study of 720 cases, however, postoperative mortality was generally quite low (approximately 0.5%). In our cohort, no deaths occurred. Current available data indicate that Ta-TME is a safe operative technique. Indeed, in our study, the median postoperative hospital stay was 9 days and comparable to those in the laparoscopic or open surgery groups. This result is consistent with the results reported by Araujo et al. for 150 patients.
Sufficient and appropriate lymph adenectomy is necessary for the accurate staging of rectal cancer and indicates the quality of the resection. Inadequate dissection of the mesorectum leads to a greater risk of residual disease and then an increased and unsatisfactory rate of local recurrence [31-34]. After neoadjuvant chemoradiation, patients have fewer lymph nodes , but in our study, the median number of lymph nodes harvested was not different between the 3 groups (7, 6, and 7 nodes per resection.).
Regarding operation time, the Ta-TME group had a significantly longer median operation time compared to the open and laparoscopic groups (302 min, 253 min, and 135 min; p<0.001). The shortest times for each of these groups were 215 min, 105 min, and 88 min, respectively. This finding could be related to the learning curve. There were 2 groups in the Ta-TME operations—the abdominal and perineal groups. The operation can be completed by 1 or 2 teams of surgeons, concurrently or sequentially. During the learning curve period, the choice of operational platform is of utmost importance. Moreover, the establishment of the pneumo-rectum with a conventional device or with a TEM platform or transanal minimally invasive surgery (Tamis) platform differed greatly in shortening operation times. The longest Ta-TME operation lasted 405 min, comparable to that reported by Araujo and colleagues [29,36]. The number of cases needed to complete the learning period has been estimated as 20–40, depending on the surgeon’s prior experience and the operating room supportive team . Optimization of protocols is necessary.
Our study had several limitations. First, although the sample size was small, all patients had a difficult anatomy. Second, all cases of Ta-TME were conducted within our learning-curve period. The longer operation times, complication patterns, and rates as well as the longer hospital stays might produce some bias. Third, this was a case-matched study that incorporated only certain factors that theoretically affected outcomes for rectal cancer patients. Some other parameters that might have made the 2 control groups either better matched or were indicative of poor matches might exist that were not included in the analysis. Finally, follow-up times were short and could not provide better long-term oncologic outcomes. Therefore, long-term follow-up is needed in terms of local recurrence, actual sphincter preservation after stoma closure, and patient-reported rectal function.
In conclusion, compared to a transabdominal open and laparoscopic approach, Ta-TME appears to result in superior insphincter preservation for patients with distal rectal cancer, especially when patients are male, have a narrow pelvis, have a high BMI and have had a course of neoadjuvant chemoradiation therapy. Our study strongly suggests that Ta-TME is a safe procedure in experienced hands that may benefit from structured training for shorter operation times. It is clear, however, that the value of Ta-TME still needs to be evaluated through larger randomized trials.