Transanal total mesorectal excision compared to laparoscopic TME for mid and low rectal cancer - current evidence

Background: Transanal total mesorectal excision (TaTME) is potentially the answer to refractory challenges in rectal cancer surgery. The surgical dissection in the deep pelvis is facilitated by a down to up approach with modern laparoscopic techniques. Potential benefits are decrease in short-term morbidity including anastomotic leakages, in conversion and colostomy rate, and better quality of specimens including less R1 rates. Long-term oncological outcome data is lacking and needs to be reviewed thoroughly. Initial (comparative) series show promising results, however there is a lack of audited data and comparative data between laparoscopic TME (LaTME) and TaTME. This review compares available data of LaTME and TaTME. Methods: A systematic review was performed in PubMed to identify papers reporting TaTME series with minimal 15 patients. A comparative set of recent large RCT data on LaTME was constructed. Weighted averages were derived from the extracted data. Primary endpoints were short-term morbidity, anastomotic leakage, conversion, pathological outcomes and local recurrences (LR). Results: The search yielded 1,093 papers, of which after the selection process resulted in the inclusion of 23 series on TaTME. To make a comparison, the four latest RCT's on LaTME were identified as a referential group. The international TaTME registry paper was presented separately to make a third comparative group. Average morbidity 31.5% and 39.6% and anastomotic leakage 6.9% vs. 8.0% both in favor of TaTME. Conversion rate was 2.0% vs. 15.7% for TaTME and LaTME respectively. Complete mesorectal integrity 86.2% vs. 81.5% and CRM+ 4.6% vs. 7.9%. Five urethral injuries (0.7%) were reported. Long-term outcomes of LRs were reported in a minority of studies with heterogeneous follow-up intervals. Conclusions: This review summarizes the data and potential benefits of TaTME. Compared to LaTME, TaTME decreases short-term morbidity, conversion, suboptimal quality of the specimen and involved CRM rate. Due to concerns about underreporting of poor outcomes, a well-designed randomized controlled trial with quality assurance and report on oncological safety is needed before widespread implementation can be justified.