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of proctored cases where an expert comes to supervise the operating surgeon. Operating room nursing staff
have also been encouraged to attend courses to help assist with the implantation of this new technique.
Concurrently, there is ongoing collection of data via voluntary registries where surgeons self-report their
own experience. This has led to further education through the presentation of this data, alongside cautionary
operative videos both at scientific conferences as well as using high quality video streaming.

Although the development of this structured process is to be commended, there are still numerous limitations
that surgeons should be aware of. Firstly, this model of education has scant evidence to prove its efficacy
in teaching surgical technique. Secondly, participation in the registries is voluntary without stringent audit
processes, meaning that the data may not be completely reliable. Thirdly, in the advent of a complication,
the use of proctoring in a legal setting is unknown. Although a few papers have proposed possible training
models and conducted preliminary evaluations, these have not had the case volume nor full educational
assessment or evaluation to make any conclusions on the success or failure of these training models [18-20] .

The authors would recommend that the adoption of this technique by any colorectal surgeon should be
implemented within units of colorectal surgeons. No surgeon should look to develop this on their own. Two
experienced surgeons should be present to form a sounding board for introductory cases. Development
of local accreditation processes, audit and a willingness to participate in the current registry are seen as
mandatory.

A paper published from our institution suggested that the learning curve on CU-SUM using quality of TME,
negative distal resection margin and circumferential resection margin suggested that the learning curve of
[21]
the case would be approximately 45-51 cases .

RESULTS AND DISCUSSION
As transanal TME is an emerging technique, long-term oncologic outcomes are not yet available. A variety
of series have been published in the literature, using surrogate histopathological parameters such as resection
margins and completeness of TME specimen as well as commenting on safety and feasibility.

[22]
Numerous papers on oncological outcomes have been released. Perdawood and Al Khefagie compared
a cohort of twenty-five patients who underwent TaTME and compared them to a case-matched cohort of
patients who had previously undergone laparoscopic TME. All patients in the TaTME group had specimens
graded as complete (80%) or nearly complete (20%), whereas 16% of the laparoscopic TME specimens were
[22]
incomplete . Similarly, the rate of positive CRM was higher in the laparoscopic TME group (16%) than the
TaTME group (4%). There were no differences between the two cohorts in length of circumferential resection
margin, distal resection margin, number of harvested lymph nodes, tumor status and lymph node status.
Another comparison between laparoscopic TME and TaTME found a higher quality mesorectum specimen
[23]
grade quality in TaTME (96%) vs. laparoscopic TME (72%) . A meta-analysis of the available data by
[24]
Ma et al. showed that TaTME had a decreased rate of a CRM positivity and a higher rate of complete TME
[24]
grade specimens compared to TaTME .
Short-term outcomes for TaTME have been thoroughly examined and reported in several case reports, case
studies and systematic reviews [24-26] . Although data is limited to observational studies, this newly developed
technique would appear to be safe and feasible based on these early outcomes. A recent systematic review of
the published case series posited that the complication rate between TaTME and open or laparoscopic TME
[24]
are similar . Most concerning, however, is the rate of otherwise rare complications such as urethral injury.
A recent publication from the TaTME registry using a total of 720 cases were analysed comprising 634
[26]
patients with rectal cancer and 86 patients with benign pathology . Five urethral injuries were reported at a
rate of 0.7%, although this is not a reflection of all TaTME cases done in the world to date. Main risk factors