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Page 2 of 6 Kim et al. Mini-invasive Surg 2019;3:33 I http://dx.doi.org/10.20517/2574-1225.2019.23

Laparoscopic or Open Resection (COLOR) II trial were a narrow pelvis (22%), obesity (10%), and tumor
[6]
fixation (9%) .

To overcome the technical difficulties associated with laparoscopic TMEs, which resulted in poor
visualization of the mesorectal planes and difficulty introducing instruments, the concept of a “bottom-
up” alternative technique (from the distal to the proximal mesorectal plane), was proposed with the first
[7]
transanal TME (TaTME) procedure performed in patients with rectal cancer in 2010 by Sylla et al. .
Before TaTME was introduced, new minimally invasive devices and innovations using the Natural Orifice
Transluminal Endoscopic Surgery technique and the Transanal Endoscopic Microsurgery method were
[8]
initiated, which made the concept possible . The transabdominal transanal proctosigmoidectomy (TATA),
[9]
which is similar to TaTMEs and was developed by Marks in 1984, introduced the bottom-up technique,
in contrast to the traditional top-down technique typically used in abdominal procedures.
In this review article, we focus on current and future East Asian perspectives. Since severely obese rectal
cancer patients are still rare in East Asian countries, there is less need for TaTMEs compared to Western
countries. The low rate of high body mass index (BMI) may be one of the reasons for the low conversion
rate of laparoscopic surgery for rectal cancer and even for mid and low rectal cancers after neoadjuvant
chemoradiotherapy compared to the high conversion rates in the COLOR II (16%) and the American
College of Surgeons Oncology Group (ACOSOG) Z6051 (11.3%) trials.

ROBOTIC TME: EFFORTS TO OVERCOME THE DIFFICULTIES OF LAPAROSCOPIC TMES
Technical limitations exist with the laparoscopic approach, especially during the distal transection of the
rectum due to limited visibility and working restrictions associated with the confined space of a narrow
[10]
pelvis . Recently, robotic surgery has been proposed as a solution to this problem. Although there is no
concrete evidence that robotic surgery has an advantage in difficult cases, robotic-assisted surgery was
introduced to address the limitations of laparoscopy, and gained acceptance due to improved visualization,
lower conversion rates, better TME quality with lower positive circumferential resection margin (CRM)
rates, and earlier recovery of genitourinary functions [11-13] .

According to our experience at Severance Yonsei University Hospital in South Korea, the robotic group
showed a lower conversion rate (0% vs. 7.1%, P = 0.003) when patients with upper rectal tumors were
[14]
enrolled . In addition, when we compared patients who only underwent robotic surgery vs. laparoscopic
surgery with coloanal anastomosis, with or without intersphincteric resections, including patients with
mean tumor heights of 5.5 cm and 4.4 cm from the anal verge, the conversion rates were 2.1% vs. 16.2%,
[15]
P = 0.020, respectively . The robotic groups showed better results in terms of open conversion rates.
In addition, when we compared patients who had robotic TMEs according to pelvimetry, there were no
differencess among easy, moderate, and difficult groups in terms of operative times, which were used as
[16]
surrogate markers for TME difficulty .
[17]
In the Robotic vs. Laparoscopic Resection for Rectal Cancer (ROLARR) trial , the overall conversion
rates were 12.2% and 8.1% for laparoscopic and robotic TME surgeries, respectively. However, 27.8% of
obese patients undergoing laparoscopic TMEs and 18.9% in the robotic TME group required conversions.
Although the robotic TME group showed better results than the laparoscopic TME group, the conversion
rates were still high. In addition to high BMI, lower rectal cancers and the male gender were associated
with increased conversion rates. Moreover, accurate identification of the distal margin and the application
of the endoscope at right angles to the rectum can be challenging in a narrow pelvis.