Resection of small polyps

Original article
Incomplete resection rate of cold snare polypectomy:
a prospective single-arm observational study
Authors
ABSTRACT
Noriko Matsuura 1, Yoji Takeuchi 1, Takeshi Yamashina1, Takashi Ito1,
Background and study aims
Kenji Aoi1, Kengo Nagai 1, Takashi Kanesaka 1, Fumi Matsui 1,
sidered to be safe for the removal of subcentimeter colorectal
Mototsugu Fujii 1, Tomofumi Akasaka1, Noboru Hanaoka 1, Koji
polyps. This study aimed to determine the rate of incomplete CSP
Higashino 1, Yasuhiko Tomita 2, Yuri Ito3, Ryu Ishihara 1, Hiroyasu
resection for subcentimeter neoplastic polyps at our center.
Iishi 1, Noriya Uedo 1
Patients and methods
Cold snare polypectomy (CSP) is con-
Patients with small or diminutive adeno-
Institutions
polyp was visible. After CSP, a 1 – 3 mm margin around the resection
1
Department of Gastrointestinal Oncology, Osaka Medical Center
site was removed using endoscopic mucosal resection. The polyps
for Cancer and Cardiovascular Diseases, Osaka, Japan
and resection site marginal specimens were microscopically eval-
Department of Pathology, Osaka Medical Center for Cancer and
uated. Incomplete resection was defined as the presence of neo-
Cardiovascular Diseases, Osaka, Japan
plastic tissue in the marginal specimen. We also calculated the fre-
Department of Cancer Epidemiology and Prevention, Center for
quency at which the polyp lateral margins could be assessed for
Cancer Control and Statistics, Osaka Medical Center for Cancer
completeness of resection.
and Cardiovascular Diseases, Osaka, Japan
Results
2
3
A total of 307 subcentimeter neoplastic polyps were re-
moved from 120 patients. The incomplete resection rate was 3.9 %
submitted 9.1.2016
(95 % confidence interval [CI] 1.7 % – 6.1 %); incomplete resection
accepted after revision 5.12.2016
was not associated with polyp size, location, morphology, or operator experience. The polyp lateral margins could not be assessed ade-
Bibliography
quately for 206 polyps (67.1 %). Interobserver agreement between
DOI http://dx.doi.org/10.1055/s-0043-100215
incomplete resection and lateral polyp margins that were inade-
Published online: 2017 | Endoscopy
quate for assessment was poor (κ = 0.029, 95 %CI 0 – 0.04). Female
© Georg Thieme Verlag KG Stuttgart · New York
sex was an independent risk factor for incomplete resection (odds
ISSN 0013-726X
ratio 4.41, 95 %CI 1.26 – 15.48; P = 0.02).
Conclusions
At our center, CSP resection was associated with a
Corresponding author
moderate rate of incomplete resection, which was not associated
Yoji Takeuchi, MD, Department of Gastrointestinal Oncology, Osaka
with polyp characteristics. However, adequate evaluation of resec-
Medical Center for Cancer and Cardiovascular Diseases, 1-3-3
tion may not be routinely possible using the lateral margin from
Nakamichi, Higashinari-ku, Osaka 537-8511, Japan
subcentimeter polyps that were removed using CSP.
Fax: +81-6-69814067
Trial registered at University Hospital Medical Information Network
[email protected]
(UMIN 000010879).
Introduction
Colorectal cancer (CRC) is the third most common cause of cancer-related mortality [1]. According to the adenoma-carcinoma
sequence [2], removal of neoplastic polyps can reduce the risk
of subsequent CRC [3, 4]. Most colorectal polyps have a diameter of 1 cm [5] and have tubular histology with low grade dysplasia [6]. Although most polyps will never become invasive
cancer [7], endoscopic removal of all detected adenomas is
standard practice during colonoscopy screening. Nevertheless,
endoscopic resection is associated with potential complications, such as delayed bleeding, coagulation syndrome, and
perforation [8 – 10]. To minimize the risk of complications during subcentimeter polyp removal, there are several promising
cold polypectomy techniques (i. e. polypectomy without elec-
Matsuura Noriko et al. Incomplete resection rate … Endoscopy
trocautery) that use biopsy forceps (cold forceps polypectomy
[CSP]) or snares (cold snare polypectomy [CSP]) [11, 12].
In a recent study, we found that CSP was a feasible method
for removing subcentimeter lesions without delayed bleeding,
although retrieval failure and inadequate assessment of the
polyp margins were common [13]. Complete polyp resection
is critical when implementing new methods for resecting colorectal lesions, as approximately 30 % of interval CRC cases are
related to incomplete polyp resection [14, 15]. Moreover, we
found that CSP was occasionally associated with difficulties in
pathologically assessing the marginal polyp tissues, which
might be related to tissue damage that is caused during the
suctioning of subcentimeter polyps through the endoscope
channel. Thus, the polyp margins may not be optimal for the
pathological evaluation of completeness of CSP resection. We
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mas (diameter 1 – 9 mm) were recruited to undergo CSP until no
Original article
Patients and methods
The fixed specimens were sectioned serially at 2 mm intervals, and then assessed by two experienced pathologists according to the Vienna classification of gastrointestinal epithelial
neoplasia [20]. Cases of incomplete resection were identified
based on the presence of any neoplastic tissue in the marginal
specimen (▶ Fig. 1). All patients were followed up at our hospital within 1 month to identify any postoperative complications.
Study participants
Study outcomes
This prospective, single-arm, observational study was performed at an endoscopy unit in a Japanese cancer referral center between March and December 2013. We recruited patients
aged ≥ 20 years who were undergoing endoscopic colorectal
polypectomy. The exclusion criteria were inflammatory bowel
disease; familial polyposis; CRC with symptoms of stenosis, active bleeding, non-correctable coagulopathy, or severe organ
failure; the use of anticoagulant therapy or antiplatelet therapy; and the absence of informed patient consent.
For this study, we only considered lesions that were detected during colonoscopy and diagnosed as adenomas with a diameter of < 10 mm. The study protocol was approved by our institutional Ethics Committee, and was registered in the University Hospital Medical Network Clinical Trials Registry (UMINCTR, UMIN 000010879). All patients provided their written informed consent before participating in the study.
The primary outcome was the rate of incomplete CSP resection
(presence of neoplastic tissue in the resection site marginal
specimens from pathologically confirmed neoplastic polyps).
We also performed subgroup analyses according to sex, age
(< 70 years/≥ 70 years), location (proximal/distal to the splenic
flexure), morphology (protruded, sessile/superficial, elevated),
polyp size (1 – 5 mm/6 – 9 mm), and operator experience (expert/senior resident). Experts were defined as having ≥ 10 years
of endoscopy experience, and senior residents were defined as
having < 10 years of experience.
The secondary outcomes were defined as the incidences of
immediate bleeding after the CSP (evident bleeding that required endoscopic hemostasis during the examination), delayed bleeding (evident bleeding that required endoscopic hemostasis after completion of the examination), pathological
characteristics of polyps, and adverse events.
Procedures
Statistics
Medications for bowel preparation and sedation were administered as previously reported [16, 17]. All procedures were performed by one of 11 experienced colonoscopists (4 experts and
7 senior residents). A standard or magnifying colonoscope was
used in all cases (EVIS CF-240I, Q260DI, FH260AZI, H260AZI,
HQ290 or PCF-Q260AZI; Olympus Medical Systems, Co., Ltd.,
Tokyo, Japan). Patients were assessed for polyp eligibility using
narrow-band imaging (NBI), and the polyp size was measured
using an open hexagonal electrosurgical snare (13 mm Captivator, Small hex type; Boston Scientific, Marlborough, Massachusetts, USA). The location, size, and macroscopic type of all detected lesions were documented according to the Paris classification [18].
Polyps that were diagnosed as Type 2 using the NBI International Colorectal Endoscopic (NICE) classification were resected
using CSP [19]. CSP was performed using an electrosurgical
snare (Captivator), and repeated CSP was allowed until no residual polyp was observed. After CSP, we injected normal saline
into the submucosal space at the base of the resection site,
and then removed the marginal specimen at the resection site
using endoscopic mucosal resection (EMR) and the same snare
that was used for CSP with a forced current mode (VIO 300D;
ERBE, Tübingen, Germany). The aim of this step was to obtain
1 – 3 mm specimens of the clear margins from the surrounding
non-neoplastic mucosa (▶ Fig. 1). The removed polyps and resection site marginal specimens were both retrieved via suction
through the colonoscope working channel, and trapped in separate bottles that were attached to the suction tube (▶ Fig. 2,
▶ Video 1). The trapped specimens were stored in separate
jars containing 10 % formalin.
The required sample sizes (patients and polyps) were calculated using a simulation approach. The number of required
polyps was estimated based on a Poisson distribution with 1.5
polyps per patient, based on the averages from our previous
data. The reported rates of incomplete resection using the
conventional method range from 3.4 % [21] to 6.8 % [5]. However, as an incomplete resection rate of 6.8 % for subcentimeter polyps seemed relatively high, we assumed a reference
standard of 3.4 % and set the noninferiority margin as + 3.4 %
(i. e. 6.8 %). Using the modified formula for calculating sample
size in noninferiority single-arm studies [22], we estimated
that a minimum of 310 polyps were needed to evaluate the
noninferiority of the alternative method using a power value
of 80 % and a one-sided alpha value of 5 %. A simulated sample
size calculation was run 10 000 times using MATLAB version
R2013a (MathWorks, Natick, Massachusetts, USA).
Results for nonparametric data were reported as median (interquartile range or range). The data structures for the polyps
were clustered according to patient, and we calculated the confidence intervals (CIs) by considering the intragroup correlations for single patients.
Multivariate mixed-effect logistic regression analysis was
used to evaluate the effects of the polyp characteristics. All
variables that were significant in the univariate analyses were
considered as potential risk factors in the multivariate logistic
regression analysis. All statistical analyses were performed
using Stata software version 13.1 (Stata Corp., College Station,
Texas, USA).
Matsuura Noriko et al. Incomplete resection rate … Endoscopy
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thought therefore that the completeness of CSP resection
should be assessed using the margins at the post-resection mucosal defect. The aim of the present study was to evaluate the
rate of incomplete CSP resection using marginal specimens following CSP.
V I D EO 1
Patients undergoing
endoscopic colorectal
polyp resection
Polyps <10 mm and
NICE Type 2
Cold snare polypectomy
Additional endoscopic
mucosal resection
Retrieval
Retrieval
Removed polyp
Marginal specimen
▶ Fig. 2 Flow diagram showing patient enrollment and study design. NICE, Narrow-band Imaging International Colorectal Endoscopic (classification).
Results
Patient recruitment and flow
During the study period, 536 patients underwent colorectal
endoscopic resection at our center, 398 of whom were excluded because they were participating in other clinical trials or because they did not fulfill the inclusion criteria. Thus, 138 patients were assessed for eligibility, and 6 patients were not in-
Matsuura Noriko et al. Incomplete resection rate … Endoscopy
▶ Video 1: Study procedures. A narrow-band image of an 8-mm
flat elevated lesion revealed adenoma. Cold snare polypectomy
was performed and the resected specimen was retrieved. Endoscopic mucosal resection was subsequently performed at the polypectomy site, and the resected specimen was retrieved.
cluded because they refused to participate or fulfilled the exclusion criteria, and 1 patient was subsequently excluded after
enrollment because she refused to participate (▶ Fig. 3). Eventually, 131 patients were screened.
We detected 375 subcentimeter polyps in the 131 patients
who were eligible for analyses; 13 polyps were excluded because they were diagnosed as non-neoplastic lesions prior to
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▶ Fig. 1 Images from a complete resection case. a An 8-mm lesion protruding into the sigmoid colon. b Narrow-band imaging (NBI) of the lesion
revealed that it was Type 2, according to the NBI International Colorectal Endoscopic classification. c Cold snare polypectomy was performed to
retrieve the polyp. d The submucosa was injected with a saline solution. e Endoscopic mucosal resection was performed at the polypectomy site,
and the marginal specimen was retrieved. f The histopathological specimen revealed a mucosal defect without any residual polyp.
Original article
Assessed for eligibility (138 patients)
▶ Table 1 Demographic and clinical characteristics of patients who
had marginal resection site specimens analyzed after cold snare polypectomy.
Excluded n = 6 (IBD 1; refusal 5)
Patients, n
120
132 patients enrolled
Male/female, n (%)
80 (66.7)/40 (33.3)
Age, median (IQR), years
70 (64 – 75)
Refusal after enrollment n = 1
131 patients screened
NICE Type 1 n = 12; SMT n = 1
362 polyps (<10 mm) in 126 patients
Total no. of polyps, n
▪ No. of polyps per patient, median
(range), n
307
2 (1 – 15)
Non-neoplastic polyp:
45 in 34 patients
317 neoplastic lesions in 123 patients
EMR
EMR failure:
5 polyps in 5 patients
Retrieval failure:
2 polyp 2 patients
Contamination:
1 polyp in 1 patient
Protocol violation:
2 polyps in 2 patients
307 evaluable marginal specimens in 120 patients
▶ Fig. 3 Flow diagram showing the inclusions of patients and
polyps. NICE, Narrow-band Imaging International Colorectal Endoscopic (classification); IBD, inflammatory bowel disease; SMT, submucosal tumor, EMR, endoscopic mucosal resection.
CSP. Thus, 362 NICE Type 2 polyps were removed from 126 patients using CSP. Among the 362 subcentimeter polyps, residual polyp was endoscopically evident in 25 lesions (6.9 %),
and these patients underwent additional CSP. EMR was then
performed at all CSP sites.
A total of 317 polyps (87.5 %) were pathologically diagnosed
as neoplastic and the resection site marginal specimens were
subsequently assessed, of which 10 could not be evaluated because of EMR or retrieval failure, contamination of the specimen after EMR, or protocol violation. Therefore, marginal specimens from 307 lesions in 120 patients were evaluated for resection completeness ( ▶ Fig. 3).
The baseline characteristics of evaluable patients and lesions
are shown in ▶ Table 1. Histopathological assessments of the
polyp lateral margins revealed that 101 (32.9 %) contained no
neoplastic tissue; the lateral margins of the remaining 206
polyps (67.1 %) could not be assessed.
Study outcomes
Among the 307 evaluable resection site marginal specimens obtained following EMR, histopathological examination revealed
that 295 (96.1 %) did not contain neoplastic tissue and 12 lesions did contain neoplastic tissue; thus, the unadjusted rate of
▪ Cecum
19 (6.2)
▪ Ascending colon
74 (24.1)
▪ Transverse colon
111 (36.2)
▪ Descending colon
31 (10.1)
▪ Sigmoid colon
63 (20.5)
▪ Rectum
9 (2.9)
Morphology, n (%)
▪ Protruded, sessile
▪ Superficial, elevated
Polyp size, median (IQR), mm
237 (77.2)
70 (22.8)
4 (3 – 6)
Polyps according to operator experience
▪ Experts (n = 4)
155 (50.5)
▪ Senior residents (n = 7)
152 (49.5)
Histological type, n (%)
▪ Adenoma
305 (99.3)
▪ Low-grade/tubulovillous/high-grade
302 (98.4)/1 (0.3)/2 (0.7)
▪ Noninvasive carcinoma
2 (0.7)
Polyp involvement in the polyp lateral margin, n (%)
▪ No neoplastic tissue in polyp lateral
margin
101 (32.9)
▪ Inadequate assessment of the polyp
lateral margin
206 (67.1)
▪ Neoplastic tissue in polyp lateral
margin
0
IQR, interquartile range.
incomplete CSP resection was 3.9 % (95 %CI 1.7 % – 6.1 %). All residual neoplastic tissues were found in the marginal mucosa,
and not at the bottom of the mucosal defect. After we accounted for the intragroup correlations in single patients, the adjusted 95 %CI was 2.2 % – 6.9 %. For the 206 removed polyps with
lateral margins that were inadequate for assessment, incomplete resection (as determined by the presence of neoplastic
tissue in the corresponding resection site marginal specimen)
was observed in 11 polyps (5.3 %). The sensitivity, specificity,
and accuracy for inadequate polyp margins to assess resection
completeness were 0.92 (95 %CI 0.65 – 0.99), 0.34 (95 %CI
Matsuura Noriko et al. Incomplete resection rate … Endoscopy
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Location, n (%)
Cold snare polypectomy
▶ Table 2 Patient- and lesion-related factors according to incomplete resection or lateral polyp margins that were inadequate for assessment
(307 polyps from 120 patients).
Incomplete resection1
Inadequate polyp margin assessment 2
P
κ (95 %CI)
12/307 (3.9)
206/307 (67.1)
< 0.001
0.029 (0 – 0.04)
10/204 (4.9)
140/204 (68.6)
< 0.001
2/103 (1.9)
66/103 (64.1)
▪ Protruded, sessile (0 – Is)
8/237 (3.4)
155/237 (65.4)
< 0.001
▪ Superficial, elevated (0 – IIa)
4/70 (5.7)
51/70 (72.9)
< 0.001
▪ 1 – 5 mm
7/223 (3.1)
145/223 (65.0)
< 0.001
▪ 6 – 9 mm
5/84 (6.0)
61/84 (72.6)
< 0.001
▪ Expert
3/155 (1.9)
91/155 (58.7)
< 0.001
▪ Senior resident
9/152 (5.9)
115/152 (75.7)
< 0.001
Overall, n/N (%)
Location, n/N (%)
▪ Proximal to splenic flexure
▪ Distal to splenic flexure
Morphology, n/N (%)
Operator experience, n/N (%)
CI, confidence interval.
1
Determined histologically by the presence of neoplastic tissue in the resection site marginal specimen.
2
Determined histologically to be inadequate for the assessment of neoplasia.
0.33 – 0.34), and 0.36 (95 %CI 0.34 – 0.37), respectively. The
kappa value for comparing lesions with incomplete resection
and polyp margins that were inadequate for assessing resection
completeness was 0.029 (95 %CI 0 – 0.04). The rates of incomplete resection and polyp margins that were inadequate for assessment were significantly different between the various subgroups ( ▶ Table 2).
Factors associated with incomplete resection
We did not observe any significant differences in age, location,
morphology, size, or operator experience when we compared
lesions with and without incomplete resection. However, female sex was an independent risk factor for incomplete resection in the multivariate analysis ( ▶ Table 3).
Adverse events
Immediate bleeding occurred in two patients (1.6 %) during the
CSP, and hemostasis was achieved using endoclips in one case
and using additional EMR in the other case. We applied prophylactic endoclips for four lesions and prophylactic coagulation
for one lesion at the post-EMR site. One patient (0.8 %) presented with immediate post-polypectomy bleeding just after the
additional EMR, and delayed bleeding occurred in six patients
(4.8 %). All seven cases of immediate and delayed post-EMR
bleeding were managed easily using endoscopic measures.
All patients visited our outpatient department a median of
13 days (range 3 – 40 days) after the procedure. Five patients
(4.0 %) complained of minor postoperative bleeding, which
stopped spontaneously without any intervention. No other
complications, such as perforation or post-polypectomy syndrome, were observed.
Matsuura Noriko et al. Incomplete resection rate … Endoscopy
Discussion
This prospective observational study revealed that CSP was
associated with a moderate rate of incomplete resection for
subcentimeter colorectal polyps. Previous studies have compared the resection rates of CSP and CFP [23, 24], and found
that CSP was associated with a higher rate of complete resection. However, as we thought that CSP could become a standard treatment for subcentimeter polyps, we aimed to identify
the rate of incomplete CSP resection using resection site marginal specimens that were obtained using subsequent EMR
after CSP. It is also important to note that the previous reports
regarding incomplete polyp resection included hyperplastic
polyps and sessile serrated adenoma/polyps [23, 24]. However,
it is often difficult to evaluate the margins of these polyps using
only endoscopy, or to determine whether incomplete resection
in these cases is related to the actual CSP technique or to the
difficulty in evaluating the polyp margins. Thus, polyps were
limited to conventional adenomas in the present study, as
these polyps have margins and residues that are more easily
evaluated after CSP.
In the present study, we performed CSP followed by subsequent EMR to leave a clear 1 – 3 mm margin of surrounding
non-neoplastic mucosa (the resection site marginal specimens). In contrast, a previous study used multiple biopsies at
the edges of the CSP site to evaluate the incomplete resection
rate [23]; however, these procedures might not be sufficient for
a thorough evaluation of CSP because the biopsy site can be deliberately manipulated to avoid the residual polyp. Thus, we believe that our use of subsequent EMR is more appropriate for
the evaluation of CSP completeness (vs. multiple biopsies), al-
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Size, n/N (%)
Original article
▶ Table 3 Factors associated with incomplete resection.
Univariate analysis
Multivariate analysis
OR (95 %CI)
P
OR (95 %CI)
P
▪ Male
1
0.01
1
0.02
▪ Female
4.59 (1.41 – 14.91)
Sex
4.41 (1.26 – 15.48)
Age, years
▪ < 70
1
▪ ≥ 70
0.79 (0.24 – 2.60)
0.7
1
0.99
0.99 (0.28 – 3.52)
Location
1
▪ Distal to splenic flexure
0.38 (0.08 – 1.81)
0.23
1
0.24
0.38 (0.07 – 1.94)
Morphology
▪ Protruded, sessile (0 – Is)
1
▪ Superficial, elevated (0 – IIa)
1.71 (0.49 – 6.02)
0.4
1
0.74
1.25 (0.34 – 4.57)
Size
▪ 1 – 5 mm
1
▪ 6 – 9 mm
1.98 (0.59 – 6.60)
0.27
1
0.31
1.90 (0.55 – 6.59)
Operator experience
▪ Expert
1
▪ Senior resident
3.19 (0.84 – 12.05)
0.087
1
0.087
3.32 (0.84 – 13.17)
OR, odds ratio; CI, confidence interval.
though careful maneuvering is needed to perform the subsequent EMR at the resection site. We also used the forced coagulation mode for EMR to avoid bleeding, although it could be
argued that the forced coagulation can cause tissue damage
outside of the marginal specimen. Nevertheless, any residual
polyp after CSP would be present immediately outside of the
CSP site, which would correspond to approximately the center
of the marginal specimen. Thus, we believe that any coagulation mode-related tissue damage would not affect the marginal
assessment of resection completeness.
Based on our moderate rate of incomplete resection (3.9 %),
it is important to consider the possibility of this outcome. Although all residual polyps were discovered in the margin of
the marginal specimen, and not in the mucosal defect itself
[25], operators should carefully observe the surrounding mucosa after CSP, by washing any minor bleeding sites using a jet
function. In addition, our subgroup analyses revealed that female sex was an independent risk factor for incomplete resection. Although we do not have a plausible explanation for this
relationship, it is possible that this finding was biased by the
small number of cases with incomplete resection. Nevertheless,
care must be taken to detect residual polyp after CSP resection,
especially when treating female patients.
The present study revealed that the lateral margins of 67.1 %
of the resected polyps were inadequate for assessment. Some
endoscopists might consider this a significant issue, although
this rate is comparable to the rate from our previous report
[13]. We believe that the cause of specimens being inadequate
for assessment might be related to retrieval through the working channel, a process that could damage the tissue and complicate precise histological assessment of the polyp lateral margins. However, only 3.9 % of the resection site marginal specimens contained residual neoplastic tissue, and the interobserver agreement was relatively poor for cases of incomplete resection and polyp lateral margins that were inadequate for assessment.
Thus, findings from the polyp lateral margins were not related to incomplete resection, which may indicate that resection
completeness cannot be evaluated routinely using the polyp
lateral margins, and that it may not be necessary to consider
the polyp margin after CSP resection of subcentimeter polyps.
In this context, a “resect and discard” concept is currently a
“hot topic” in this field of polyp management [26], and polyp
involvement at the polyp margins cannot be assessed when
the resected specimen is discarded. Given that our results suggest that polyp lateral margins are not useful in assessing resection completeness, our study findings can be used to support
the “resect and discard” concept.
This study has several limitations. First, the rate of incomplete CSP resection was not compared with the rates for other
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▪ Proximal to splenic flexure
www.bsg.org.uk/clinical-guidance/endoscopy/colonoscopic-polypectomy-and-endoscopic-mucosal-resection-a-practical-guide.html
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techniques (e. g. conventional EMR or hot biopsy), because we
cannot confirm the safety of the additional EMR after conventional EMR as a reference standard. However, we believe that
similar incomplete CSP resection rates in previous reports validate our present results [23, 24]. Second, we evaluated the histological results of resected specimens from the EMR site, but
we did not evaluate the rate of residual polyps after CSP at the
follow-up endoscopy. Third, some of the patients had multiple
lesions, which we resected and retrieved using a polyp trap.
Thus, we cannot exclude the possibility that one specimen
might have become contaminated by the previous specimen,
and it is possible that the rate of incomplete CSP resection
found in the study was higher than the actual rate of incomplete resection. Fourth, we used a nondedicated conventional
snare in this study because it would have been too expensive
to use a dedicated snare for CSP and then a nondedicated conventional snare for conventional EMR. Thus, it is possible that
we might have achieved a lower incomplete resection rate if
we had used a dedicated snare [27]. Fifth, we used a single-center design, which is associated with known risks of bias. Therefore, large-scale, multicenter, prospective studies are needed
to investigate the actual rate of residual polyps after CSP.
In conclusion, this study revealed an incomplete resection
rate of 3.9 % (95 %CI 1.7 % – 6.1 %) when we used CSP to remove
subcentimeter colorectal polyps at our center. However, the
polyp lateral margin evaluability was not related to the rate of
incomplete resection, and it may not be possible to routinely
and adequately assess the completeness of polyp resection
using the polyp lateral margins. Therefore, the resection site
margin should be carefully examined to confirm whether radical resection has been achieved when using CSP to remove subcentimeter colorectal polyps.