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Suwa et al. Mini-invasive Surg 2022;6:20 https://dx.doi.org/10.20517/2574-1225.2021.123 Page 3 of 11

Considering the above reports and referring to the American Gastroenterological Association, the European
[6-8]
Society of Gastrointestinal Endoscopy (ESGE), and the Japanese guidelines , CSP is indicated for
colorectal polyps that are nonpedunculated superficial tumors less than 10 mm in size.

CSP for SNADETs in our institution
We considered CSP to be also suitable for small duodenal lesions, and it has been performed in our
[9]
institution for endoscopic adenomas less than 10 mm in size since 2015 . The typical case treated with CSP
is a 0-IIa adenoma in the Paris classification, 6 mm in size, and located in the 2nd portion. An example of
this type of case is presented in Figure 1.

Between January 2015 and July 2021, 64 lesions in 58 patients [male/female, 44/14; median age, 67 years
(range, 39-82 years)] were resected by CSP at the Shizuoka Cancer Center. Overall, 7 lesions were in the
bulbs, 55 were in the 2nd portion, and 2 were in the 3rd portion. The median size of the lesions was 6 mm
(range, 2-12 mm). In total, 7 lesions had the macroscopic type of 0-I in the Paris classification, 50 were 0-IIa,
3 were 0-IIa+IIc, and 4 were 0-IIc. A preoperative biopsy was performed before CSP in 28 lesions (43.8%).

Regarding the short-term outcomes, the median procedure time (from the end of observation to the
completion of resection) was 3 (range, 1-23) min. The en bloc resection rate was 96.9% (62/64). During this
period, CSP was attempted for 64 lesions, but 5 lesions could not be resected without electrocautery (the
CSP completion rate was 92.2%). The characteristics of the five incompletely resected lesions are described
in Table 1. When the risk factors for incomplete resection were examined by evaluating predictive factors
such as lesion site, gross tumor type, tumor size, availability of a preoperative biopsy, and the
histopathological diagnosis, only the lesion size was found to be a statistically significant risk factor (P =
0.045, Mann-Whitney U test). However, the sample size was very small, and further investigations are
needed.

At our institution, prophylactic clipping after CSP was performed in 37 lesions (57.8%), and the percentage
of spurting bleeding immediately after CSP was 0%. No adverse events or delayed complications were
observed. The necessity of prophylactic clipping after CSP is controversial. Hamada et al. reported no
[10]
complications in patients with FAP when large numbers of polyps were resected at once without
prophylactic clipping. We usually perform prophylactic clipping after CSP for the following reasons: the
clipping procedure is easy because the lesions are diminutive lesions; the mucosal defects are small after
CSP; and the mucosa is soft without submucosal injections.

The median size of the resected specimens was 6 mm (range, 2-22 mm), and the histopathological
evaluations revealed 50 adenomas, 4 adenocarcinomas (intramucosal), and 10 nonneoplastic lesions. Of the
54 neoplastic lesions (adenomas and adenocarcinomas), the horizontal margin (HM) was negative in 27
lesions, positive in 1 lesion, and indeterminate in 26 lesions; for the vertical margin (VM), 48 lesions were
negative, 1 lesion was positive, and 5 lesions were indeterminate. It has been reported that the submucosal
tissue is not sufficiently resected in colorectal CSP specimens , and similar results might be expected in
[11]
duodenal specimens. As a result, CSP could resect only the mucosal layer when using mechanical
strangulation without electrocautery. Therefore, we think that CSP is inappropriate for cancers in which
definitive en bloc resection is desirable because it is not able to reliably resect the submucosa and to ensure
an en bloc resection with a VM0.

Regarding the long-term outcomes, 49 of 64 lesions were followed-up endoscopically for more than one
month. The median observation period was 24 months (range, 1-64 months). Local recurrence was