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De Rosa et al. Mini-invasive Surg 2020;4:34 I http://dx.doi.org/10.20517/2574-1225.2019.53 Page 5 of 12

Current practice suggests that selection of patients for TaTME includes a wider group of patients, particularly
with regard with tumor location, as we can observe with the experience of Lacy or in the International
Registry where tumors were proximally located in 20.7% and 38% of patients, respectively [28,29] , however this
remains primarily a technique for those requiring TME.

Appropriate patient selection is of paramount importance, especially during the early learning curve and
it is wise not to select very difficult cases before competence is reached. In this respect, expanding the
indications for TaTME to include those patients who could easily be done laparoscopically may be required
for training purposes.

PERIOPERATIVE RESULTS
Feasibility and safety of perioperative outcomes of TaTME have been extensively reported as well as
limitations and shortcomings that need to be addressed.

Reduced estimated blood loss, shorter hospital stay, and lower readmission rates were recently reported in
[30]
a meta-analysis of 17 studies .

Compared to laparoscopic TME, a lower rate of conversion to open surgery has been observed, ranging
between 0% and 9.1% [22,31,32] . This correlated to the level of experience, as highlighted by Dejien and colleagues
who compared low-volume centers performing TaTME (< 30 cases) to high-volume centers (> 30 cases)
[33]
and reported conversion rates of 4.3% and 2.7%, respectively .
Conversions during TME surgery are usually due to technical difficulties related to high body mass index
[32]
(BMI) and the narrow male pelvis. Ma et al. showed that this accounted for 25% of conversions in
TaTME patients vs. 47% in those undergoing laparoscopic TME. In most reported series, the occurrence of
intraoperative complications provoke conversion, with tumor or patient features not directly affecting the
operation outcome.

[34]
TaTME has also been shown to have a significantly shorter operation time, compared to laparoscopy ,
[35]
and this is even more pronounced if the operation is performed with a simultaneous two-team approach .

Concerning morbidity, several retrospective series or cohort studies reported on safety of TaTME, showing
[36]
postoperative complication rates comparable with conventional laparoscopic or open TME data .
[29]
The international TaTME registry including 720 patients reported an overall morbidity of 32.5% , in line
with several other monocentric series on TaTME [22,37] .

In a recent systematic review, TaTME and laparoscopic TME showed similar rates of intraoperative
[32]
complications, although a lower rate of postoperative morbidity was reported in the transanal group .

Several publications report a low incidence of anastomotic leak rate following TaTME, which in the largest
meta-analyses available ranges between 5.7% and 6.1% [33,38] and is similar to the results reported after
[39]
conventional TME .
Recently updated data from the multi-institutional International TaTME registry on 1594 patients over
[40]
30 months show an overall 30-day anastomotic leak rate of 7.8% , not too far from the rate of 10%
[32]
reported by Ma et al. in their systematic review.