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Ghuman et al. Mini-invasive Surg 2020;4:84 I http://dx.doi.org/10.20517/2574-1225.2020.88 Page 3 of 6

One meta-analysis that included 12 studies (11 case-control and only 1 RCT) did find a higher complete
TME in robotic vs. laparoscopic surgery (odds ratio of 1.83, P = 0.03), however there was significant
2
[16]
heterogeneity noted in the analysis (I = 47%) . Furthermore, this analysis included a majority of case-
control studies, which are of lower level of evidence, while other meta-analyses have included more RCTs
and prospective studies.

Lymph node harvest
The current guidelines, including those of the American Joint Committee on Cancer (AJCC) and College of
American Pathologists (CAP), recommend a minimum of 12 lymph nodes be examined to accurately stage
rectal cancer in order to aid in the decision for adjuvant treatment [17-19] . The reasons for low lymph node
harvest can include neoadjuvant treatment, lack of high ligation of the vessels, and potentially poor surgical
or pathologic technique. When comparing surgical approaches for rectal cancer, it is important to evaluate
lymph node harvest with each technique.

The ROLARR RCT performed an intention to treat analysis in which one of the outcomes measured was
median lymph nodes retrieved . They reported no differences; both groups yielded a high number of
[10]
[11]
lymph nodes: 24.1 (laparoscopic) vs. 23.2 (robotic), almost double the minimal requirement. Kim et al.
noted a higher number of lymph nodes in the robotic (median 18) compared to the laparoscopic group
(median 15) (P = 0.04) in their RCT. They also examined the rate of 12 or more lymph nodes retrieved in
their groups and found 90.9% of patients achieved this benchmark in the robotic group compared to 74%
of patients in the laparoscopic group. Of note, the majority of patients in this single-center RCT received
preoperative chemoradiation (77.3% in robotic vs. 77.5% in laparoscopic), which might have led to the
lower number of lymph nodes.

A seven-institution multicenter study examined consecutive patients who underwent robotic or
[20]
laparoscopic intersphincteric resection for low rectal cancer . Propensity score analysis was performed
with 1:1 case-match, in which no difference was found in the number of lymph nodes retrieved (P = 0.126)
or the number of positive lymph nodes (P = 0.712). Kim et al. also used propensity score matching to
[21]
analyze their retrospective cohort and, after matching, found no difference in the number of harvested
lymph nodes (P = 0.44). Furthermore, a propensity score match study was performed in consecutive obese
patients who underwent laparoscopic or robotic rectal resection at three centers, and no difference was
noted in the mean lymph node yield (17 in robotic vs. 16 in laparoscopic, P = 0.639) . A single-center
[22]
study examined their prospectively collected database of mid to - distal rectal cancers and found a higher
[23]
median number of lymph nodes harvested (12 in laparoscopic vs. 14 in robotic, P = 0.002) . However, the
groups however were not matched between the median tumor distance of 8 cm in laparoscopic vs. 7 cm in
robotic. Moreover, there were more male patients, more comorbidities, and preoperative radiation in the
robotic surgery group.

Multiple meta-analyses examining the highest level of evidence available in the form of RCTs have found
no difference in the number of lymph nodes retrieved when comparing laparoscopic and robotic surgery
for rectal cancer [13-15,24,25] .

Margins
Rectal cancer specimen margins assessed are circumferential radial (CRM), proximal, and distal. Ensuring
negative margins is of utmost importance in reducing local recurrence rates. Margin assessment is used
as a marker to examine and compare surgical techniques. The literature on robotic vs. laparoscopic rectal
resection for each margin status is discussed below.

Circumferential Radial Margin: The largest RCT to date on robotic vs. laparoscopic resection for rectal
[10]
cancer is the ROLARR trial . In total, 237 patients were randomized to robotic, of whom the CRM