Introduction
Colorectal cancer (CRC) is the third most common cancer in the world, and the incidence
of CRC is rising rapidly in many Asian countries [1]. CRC development is considered to occur mainly via the adenoma – carcinoma sequence
[2], and the development of CRC is effectively reduced by colonoscopy with polypectomy
[3]. More than 90 % of polyps detected at colonoscopy are small (6 – 9 mm) or diminutive
(≤ 5 mm), with most being diminutive [4]. The main reason for resecting small adenomas and sending them for histopathologic
examination is to provide guidance on the appropriate intervals for future surveillance
[5]. Being able to diagnose adenomas in vivo would allow for them to be resected and
discarded, eliminating the costs associated with histopathology.
Narrow-band imaging (NBI) is an optical endoscopic imaging technology that highlights
the superficial mucosal vasculature, thereby accentuating and highlighting the surface
pattern of polyps. These patterns can help characterize polyp histology [6]. In the “resect and discard” strategy proposed by Ignjatovic et al. [4], the surveillance interval is decided based on optical diagnosis (OD) using non-magnifying
NBI without formal histopathology. The “resect and discard” strategy has the potential
to change the standard management of small polyps, with a major reduction in the cost
of screening and surveillance colonoscopy [7]. However, it carries the risk of discarding small advanced lesions (SALs), which
are small (< 10 mm) lesions with advanced histology (villous component, high grade
dysplasia, and adenocarcinoma), as even small lesions may contain advanced features
or cancer [8]. Although it is rare, the “resect and discard” strategy has a risk of discarding
small invasive cancer that should be evaluated for its pathological characteristics
to consider additional surgery.
OD using magnifying NBI (M-NBI) reportedly enables the assessment of dysplasia or
the presence of colorectal neoplastic invasion, as well as differentiation between
neoplastic and non-neoplastic lesions [9]
[10]. Takeuchi and colleagues proposed that their “resect and discard” strategy using
M-NBI could reduce the risk of discarding SALs, including small invasive cancer, as
M-NBI provides more accurate diagnosis of SALs and enables the distinction between
neoplastic and non-neoplastic lesions [11]
[12]. The “resect and discard” strategy using M-NBI could be an attractive concept for
patients, gastroenterologists, and health service providers.
To our knowledge, there are few reports on the mid- to long-term outcomes, including
recurrence rate and survival rate, after performing the “resect and discard” strategy
using M-NBI for small colorectal polyps. The aim of the present retrospective study
was to clarify the short- and mid-term outcomes of the “resect and discard” strategy
for small (< 10 mm) colorectal polyps.
Patients and methods
Patients
The clinical records were reviewed from 501 consecutive patients who underwent the
“resect and discard” strategy for small colorectal lesions at our hospital between
January 2008 and December 2010. The inclusion criterion was the use of the “resect
and discard” strategy for the management of colorectal polyps smaller than 10 mm on
the basis of evaluation using M-NBI. Exclusion criteria included: colorectal polyps
equal to or larger than 10 mm, evidence of familial adenomatous polyposis, hereditary
non-polyposis CRC, or inflammatory bowel disease; presence of active malignant diseases
in any other organs; presence of synchronous or metachronous advanced CRC; and patient
age older than 85 years. We analyzed the short-term outcomes of all 501 patients who
underwent the “resect and discard” strategy on the basis of baseline and short-term
outcome data collected prospectively on a computer database. For the analysis of mid-term
outcomes, we excluded 25 patients with less than 1 year of follow-up data, leaving
476 patients who were treated between 2008 and 2010. Mid-term outcome data were retrospectively
collected from electronic medical records (in the period between November and December
2017).
The present retrospective study was conducted at our hospital in Japan. The institutional
review board of our hospital approved the collection of data, examination of past
cases, and submission of the results of the present study, and written informed consent
was obtained from all patients.
Premedication and procedures
All patients were prepared for colonoscopy by the oral administration of 2 to 3 L
of polyethylene glycol/electrolyte solution. To prevent bowel movements, 10 mg of
scopolamine butylbromide or 0.5 mg of glucagon was intravenously administered to patients
without contraindications before examination. All procedures were performed by 10
endoscopists who had each previously conducted more than 1000 colonoscopies. All of
the endoscopists were familiar with M-NBI of gastrointestinal lesions, as they all
had more than 1 year of experience with the technique. We used the electronic endoscopy
system with NBI (Evis Lucera Spectrum System, Olympus, Tokyo, Japan) and high-resolution
optical magnifying colonoscopes (Evis CF-H260AZI or PCF-Q260AZI; Olympus). To facilitate
the identification and diagnosis of colonic lesions, M-NBI or magnifying chromoendoscopy
with 0.05 % Crystal Violet was used in addition to white-light observation. Lesions
were detected using the white-light mode. The location, size, and macroscopic type
of all detected lesions were documented according to the Paris classification [13]. The size of the detected lesion was measured using 2.2-mm closed biopsy forceps
(Radial Jaw 4: Boston Scientific, Boston, MA, United States) or a mini snare (10 mm
diameter, oval snare, Olympus). Small polyps were defined as those that were less
than 10 mm in diameter. When the detected lesion was a small polyp, all colorectal
lesions were evaluated in real time via M-NBI after assessment using conventional
white-light imaging (C-WLI). The endoscopists predicted the type of polyp (non-neoplastic,
low grade adenoma, suspected SAL, or inconclusive) using M-NBI. The prediction of
polyp type was used to decide polyp management.
Magnifying narrow-band imaging-assisted optical assessment and polyp management
Following C-WLI, all colorectal lesions were evaluated by M-NBI. Diagnosis according
to M-NBI was based on Sano’s capillary classification [14], and the microvascular architecture was classified into three types according to
the capillary pattern (CP) (CP type I, II, or III). The CP assessed by M-NBI is useful
for differentiating small colorectal non-neoplastic polyps from neoplastic polyps
[15], and is highly accurate at distinguishing between low grade dysplasia (LGD) and
high grade dysplasia (HGD) or invasive cancer; thus, the CP can be used to predict
the histopathology of colorectal neoplasia [10]. CP type I is indicative of hyperplastic polyps (HPs), CP type II is indicative
of LGD, and CP type III is indicative of HGD or invasive cancer [10]
[15]. Diminutive tumors with depressions have a high frequency of carcinoma and submucosal
invasion [8]. Low grade adenoma predicted with high confidence was defined according to the following
endoscopic conditions ([Fig. 1a]): 1) the absence of a depressed area within the lesion under careful C-WLI, and
2) CP type II under M-NBI.
Fig. 1 a An example of low grade adenoma imaged with typical magnifying narrow-band imaging.
i Endoscopic findings using conventional endoscopy with white-light imaging. A reddish,
slightly elevated lesion (6 mm in diameter) is observed in the sigmoid colon. ii Endoscopic findings using magnifying narrow-band imaging. Capillary pattern II was
defined as microvascular architecture arranged in a round, oval, or honeycomb-like
pattern. iii The final histological diagnosis was low grade adenoma. b An example of submucosal invasive cancer viewed by endoscopic modalities. i Endoscopic findings using conventional endoscopy with white-light imaging. A reddish,
protruding lesion with a shallow depressed area (8 mm in diameter) is observed in
the sigmoid colon. ii Magnifying narrow-band imaging containing visible microvascular architecture and
high microvessel density with lack of uniformity and irregularity, indicative of capillary
pattern III. iii The final histological diagnosis was submucosally invasive cancer (930 μm) with blood
vessel invasion. c An example of submucosal invasive cancer viewed by endoscopic modalities. i Endoscopic findings using conventional endoscopy with white-light imaging. A reddish,
slightly depressed lesion (5 mm in diameter) is observed in the rectum. ii Magnifying narrow-band imaging showing thick and irregular vessels and the presence
of a nearly avascular region, indicative of capillary pattern III. iii The final histological diagnosis was submucosally invasive cancer (590 µm) with lymphatic
and blood vessel invasion.
When the detected lesion was a small polyp (< 10 mm), the polyp type (non-neoplastic,
low grade adenoma, suspected SAL, or inconclusive) was predicted by the endoscopists
using M-NBI following C-WLI, with their diagnostic confidence rated as high or low.
One of three types of polyp management (“leave in situ”, “resect and discard”, or
“resect and send” for formal histopathology) was decided upon in accordance with the
prediction of polyp histology. In the case of presumably non-neoplastic lesions located
in the rectosigmoid colon, endoscopists were not required to remove the lesions, as
per the “leave in situ” option. In the case of low grade adenoma predicted with high
confidence, endoscopists discarded the polyp without histological assessment, as per
the “resect and discard” option. In the case of SALs, including small invasive cancer
([Fig. 1b, c]), polyps where there were difficulties in predicting type, or polyps for which OD
was made with low confidence, endoscopists resected and sent the lesions for formal
histopathology, as per the “resect and send” option. While non-neoplastic polyps located
in the right-sided colon or descending colon can potentially be sessile serrated adenoma/polyps,
such polyps were also managed via the “resect and send” strategy in the present study.
An algorithm for the management of small polyps (< 10 mm) using M-NBI following C-WLI
is shown in [Fig. 2]. M-NBI was used in all cases to confirm that there was no residual tumor in the
post-endoscopic resection ulcer site.
Fig. 2 An algorithm for the management of small polyps (< 10 mm) using magnifying narrow-band
imaging following conventional white-light imaging.
Validation of magnifying narrow-band imaging for classifying colorectal polyps
M-NBI observation was performed at our hospital between January 2007 and December
2007. During this time period, there were 425 consecutive cases of colorectal lesions
that had been endoscopically or surgically resected; these cases were retrospectively
analyzed. On the basis of histological characteristics, the 425 lesions were identified
as: HPs/sessile serrated polyps (n = 33 lesions), LGD such as tubular adenoma/tubulovillous
adenoma (n = 316 lesions), HGD (n = 60 lesions), superficial submucosal invasive (SM-s)
carcinoma located less than 1000 µm below the mucosa (n = 5 lesions), and deep submucosal
invasive (SM-d) carcinoma located deeper than 1000 µm (n = 11 lesions). We evaluated
the relationship between the CP classification and the histologic findings of these
lesions.
Clinical outcomes
To evaluate the efficacy and safety of the “resect and discard” strategy, we analyzed
the following short-term outcomes: 1) en bloc resection rate, 2) postoperative bleeding
rate, and 3) perforation rate. To validate curability using the “resect and discard”
strategy, we evaluated the following mid-term outcomes: 1) overall survival rate,
2) disease-specific survival rate, 3) local recurrence rate, and 4) distant recurrence
rate. Data are presented as median (range) or mean ± standard deviation. Survival
time was calculated as the interval between the date of the treatment and the date
of death or, for survivors, the last date on which they were confirmed to be alive.
In principle, surveillance colonoscopy was performed once a year after the initial
colonoscopy to detect local recurrence and new lesion occurrence. As post-endoscopic
resection ulcer scars were not recognized in most cases, local recurrence was defined
as the presence of adenomatous or carcinomatous tissue on follow-up examination at
or near the site of prior endoscopic treatment. Follow-up computed tomography (CT)
of the abdomen and pelvis was not scheduled; however, many included patients underwent
CT of the abdomen and pelvis for other reasons during the follow-up period. In these
cases, we assessed the presence of lymph node or distant metastasis.
Post-colonoscopy colorectal cancer (PCCRC) rates have been proposed as a key quality
indicator of colonoscopy procedures [16]. We investigated the occurrence of PCCRC during the follow-up period in the present
study. Based on a previous research method, we defined PCCRC as CRC that had been
diagnosed 7 to 36 months after colonoscopy, when no cancer had been detected before
the procedure [17]. CRC was defined as a tumor that had penetrated through the muscularis mucosae into
the submucosa, in accordance with the classification of the World Health Organization.
Statistical analysis
Overall and disease-specific survival rates were retrospectively assessed and calculated
using the Kaplan – Meier method. All statistical analyses were performed with EZR
(Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical
user interface for R (The R Foundation for Statistical Computing, Vienna, Austria);
more precisely, it is a modified version of R commander designed to add statistical
functions frequently used in biostatistics [18].
Results
Characteristics of the patients and the small (< 10 mm) lesions
The present study included 501 consecutive patients with 816 lesions ([Table 1]). The mean patient age was 64.5 ± 9.6 years, and the mean size of the detected lesions
smaller than 10 mm was 5.6 ± 1.6 mm. Among these lesions, 444 (54 %) were diminutive
(≤ 5 mm), and 372 (46 %) were small (6 – 9 mm). The morphological structure of the
lesions was: 785 polypoid (0-I); 31 slightly elevated (0-IIa); and no depressed lesions
(0-IIc, 0-IIa + IIc). There were 484 (59 %) polyps located proximal to the splenic
flexure, while 332 (41 %) were situated distal to the splenic flexure.
Table 1
Clinicopathological features of the patients and the small (< 10 mm) lesions.
|
Total (n = 816)
|
|
Total no. of patients
|
501
|
|
Male, n (%)
|
377
|
(75.2)
|
|
Female, n (%)
|
124
|
(24.8)
|
|
Age, mean ± SD, years
|
64.5 ± 9.6
|
|
Lesion size, mean ± SD, mm
|
5.6 ± 1.6
|
|
|
444
|
(54.4)
|
|
|
372
|
(45.6)
|
|
Macroscopic type, n (%)
|
|
|
74
|
(9.1)
|
|
|
711
|
(87.1)
|
|
|
31
|
(3.8)
|
|
|
0
|
(0)
|
|
Location, n (%)
|
|
|
39
|
(4.8)
|
|
|
213
|
(26.1)
|
|
|
232
|
(28.4)
|
|
|
86
|
(10.5)
|
|
|
177
|
(21.7)
|
|
|
69
|
(8.5)
|
SD, standard deviation.
Diagnostic performance of magnifying narrow-band imaging analysis
The relationship between M-NBI findings and the histologic features of the colorectal
lesions is shown in [Table 2]. Histologically, 100 % (29 /29) of CP type I lesions were identified as HP. In addition,
1.1 % (4 /358), 87.4 % (313 /358), and 11.5 % (41 /358) of CP type II lesions were
identified as HP, LGD, and HGD/SM-s carcinoma, respectively. Moreover, 7.9 % (3 /38),
63.2 % (24 /38), and 28.9 % (11 /38) of CP type III lesions were identified as LGD,
HGD/SM-s carcinoma, and SM-d carcinoma, respectively. M-NBI provided a sensitivity
of 99.1 % and a specificity of 46.1 % in differentiating LGD from HGD/invasive cancer,
and the overall accuracy was 88.9 %. The positive predictive value was 88.5 %, and
the negative predictive value was 92.1 %. No CP type II lesion was diagnosed as SM-d
carcinoma.
Table 2
Relationship between Sano’s capillary classification and the histological findings
in colorectal lesions examined during 2007.
|
Capillary pattern
|
n (%)
|
Pathological diagnosis, n (%)
|
|
Hyperplastic polyps
|
LGD
|
HDG
|
SM-s
|
SM-d
|
|
Type I
|
29
|
(100)
|
29
|
(100)
|
0
|
(0)
|
0
|
(0)
|
0
|
(0)
|
0
|
(0)
|
|
Type II
|
358
|
(100)
|
4
|
(1.1)
|
313
|
(87.4)
|
40
|
(11.2)
|
1
|
(0.3)
|
|
|
|
Type III
|
38
|
(100)
|
|
|
3
|
(7.9)
|
20
|
(52.6)
|
4
|
(10.5)
|
11
|
(28.9)
|
|
Total
|
425
|
33
|
316
|
60
|
5
|
11
|
LGD, low grade dysplasia; HDG, high grade dysplasia; SM-s, superficial submucosal
invasive carcinomas (< 1000 μm); SM-d, deep submucosal invasive carcinomas (≥ 1000 μm).
Short-term outcomes
En bloc resection was achieved in 100 % of cases. No adverse events (such as perforation
and delayed bleeding) occurred after the “resect and discard” strategy.
Mid-term outcomes and patient clinical course
The mid-term outcomes were examined in 476 patients who were reliably followed-up
for at least 1 year after undergoing the “resect and discard” strategy. The median
observation period was 83 months (range 12 – 117 months). [Fig. 3] shows the long-term survival rate determined using the Kaplan-Meier method. The
overall survival rate of patients who underwent the “resect and discard” strategy
is shown in [Fig. 3a]. During the follow-up period, all 15 patient deaths were caused by diseases other
than CRC. Causes of death were cerebral hemorrhage (n = 2), pharyngeal cancer (n = 2),
esophageal cancer (n = 1), gastric cancer (n = 1), liver cancer (n = 1), lung cancer
(n = 2), pancreatic cancer (n = 1), acute myocardial infarction (n = 2), hematological
malignancy (n = 2), and sudden death of unknown cause (n = 1). None of the patients
died from CRC related to the procedure, resulting in a disease-specific survival rate
of 100 % ([Fig. 3b]). Among the 476 patients who underwent the “resect and discard” strategy, there
was no local recurrence detected in the 293 patients (62 %) who underwent follow-up
colonoscopy, and no distant recurrence detected in the 309 patients (65 %) who underwent
CT of the abdomen and pelvis during the follow-up period. Overall, the median follow-up
periods during which patients received colonoscopy and CT of the abdomen and pelvis
were 61 months and 70 months, respectively. Only one CRC was diagnosed between 7 and
36 months after colonoscopy in the 293 patients who underwent follow-up colonoscopy,
and so the PCCRC rate was 0.3 % (1 /293). The PCCRC was endoscopically resected, and
was histologically diagnosed as a SM-s carcinoma.
Fig. 3 a Kaplan-Meier curves for overall survival rates after the “resect and discard” strategy
for small (< 10 mm) colorectal polyps in 476 patients. b Kaplan-Meier curves for disease-specific survival rates after the “resect and discard”
strategy for small (< 10 mm) colorectal polyps in 476 patients.
Discussion
We achieved excellent mid-term outcomes after the “resect and discard” strategy using
M-NBI following C-WLI for small (< 10 mm) colorectal polyps. The present study shows
that M-NBI following C-WLI results in appropriate evaluation of SALs, and confirms
that the “resect and discard” strategy using M-NBI is feasible and acceptable. There
was no local recurrence or distant metastasis detected in patients who underwent the
“resect and discard” strategy.
In vivo OD at the time of colonoscopy is an attractive approach for physicians, patients,
and health-care providers. The original “resect and discard” strategy involving OD
using non-M-NBI proposed by Ignjatovic et al. [4] did not take advanced histology into consideration, whereas the US Multi-Society
Task Force guidelines for colonoscopic surveillance include advanced histology as
one of the factors required for determination of the surveillance interval [5]. Takeuchi et al. reported that the “resect and discard” strategy using M-NBI reduces
the risk of discarding SALs, including small invasive cancers [12]. CP observation using M-NBI provides high accuracy for distinguishing between LGD
and HGD/invasive cancer, and thus can be used to predict the histopathology of colorectal
neoplasia in vivo [10]. Our validation results in the present study show a high level of accuracy for OD
using CP to distinguish between LGD and HGD/invasive cancer; CP type II had an overall
accuracy of nearly 90 %, and there was no SM-d carcinoma in CP type II lesions. Depressed
tumors have a significantly higher frequency of carcinoma and submucosal invasion
regardless of tumor size, so it is important to carry out careful observation to ensure
the detection of all diminutive depressed tumors [8]. Therefore, LGD predicted with high confidence was defined according to the following
endoscopic conditions: 1) the absence of a depressed area within the lesion under
C-WLI, and 2) CP type II under M-NBI.
Many clinical studies on M-NBI classifications (such as Sano’s capillary classification)
advocated in Japan have reported the usefulness of M-NBI for qualitative and quantitative
diagnosis of colorectal lesions [19]. The Japan NBI Expert Team (JNET) established in 2011 unified four previous M-NBI
classifications (the Sano, Hiroshima, Showa, and Jikei classifications), and has proposed
a universal M-NBI endoscopic classification of colorectal tumors [20]. Regardless of the gross type, the JNET classification provides useful criteria
for optical histological diagnosis of colorectal lesions, and is expected to contribute
to daily colonoscopic practice. The JNET classification could not be used in the present
study, as it was a retrospective study; further studies are required using the JNET
classification.
The recently proposed Preservation and Incorporation of Valuable Endoscopic Innovations
(PIVI) statement issued by the American Society of Gastrointestinal Endoscopy (ASGE)
suggested that the resect-and-discard model could be implemented if a minimum accuracy
and negative predictive value could be achieved [21]; this aim may be facilitated by the introduction of new generation colonoscopes
with improved optics, high definition, and fixed zoom functioning such as M-NBI. A
previous meta-analysis assessing the ASGE PIVI statement indicated that optical biopsy
technology using NBI can meet this PIVI threshold, and supports a “resect-and-discard”
strategy for colorectal adenomas ≤ 5 mm [22]. We think that the target lesion for the “resect and discard” strategy should be
carefully discussed. Some studies have reported on diminutive invasive carcinoma,
although the prevalence of diminutive invasive carcinoma is quite low [23]
[24]. Hotta et al. reported the presence of diminutive submucosally invasive cancers
of the colon and rectum; therefore, careful endoscopic observation is strongly recommended
when adopting the “resect and discard” strategy [25]. M-NBI is effective for the precise diagnosis of invasion depth in CRC [26]. Hence, although the “resect and discard” strategy involving OD using non-M-NBI
carries the risk that small invasive carcinomas may be discarded, the “resect and
discard” strategy involving OD using M-NBI has the potential to prevent such small
invasive carcinomas from being discarded.
The efficacy of colonoscopy with polypectomy to reduce CRC incidence and mortality
has been demonstrated by the US National Polyp Study published in 1993, in which a
cohort of patients undergoing colonoscopy with polypectomy of neoplasia had a 76 – 90 %
reduction in CRC incidence [3]; this same cohort experienced a 53 % reduction in mortality associated with CRC
[27]. Sending diminutive and small polyps for formal histopathology is time consuming
and resource intensive, and results in an inevitable delay in providing patients with
advice about future surveillance intervals. In cases involving multiple polyps throughout
the colon, it is sometimes difficult to retrieve and submit all polyps for formal
histologic assessment. The primary benefit of the “resect and discard” strategy is
the cost savings that can be achieved by reducing the number of polyps that are sent
for histopathological examination [28]
[29]. The potential cost savings of not sending diminutive polyps for formal histopathology
is thought to exceed $ 1 billion USD per year in the United States [29]; even greater cost-effectiveness will be achieved by also applying the “resect and
discard” strategy to small (< 10 mm) polyps, rather than just to diminutive (≤ 5 mm)
polyps. The Japanese guidelines indicate that diminutive (≤ 5 mm) neoplastic lesions
without carcinomatous findings may be left untreated, and just followed-up [30], and recent reports have shown that removal is not necessarily required for diminutive
low grade adenoma (≤ 5 mm) detected and characterized using magnifying chromoendoscopy
[31]
[32]. A large, multicenter, prospective study and a clinical trial using M-NBI are required
to validate these results.
The Japanese Society of Gastroenterology guidelines [30] recommend that follow-up colonoscopy should be done within 3 years after endoscopic
resection (ER), in accordance with the pilot data of the Japan Polyp Study [33]. The Japan Polyp Study was a large multicenter prospective cohort study carried
out to determine the appropriate interval period for surveillance colonoscopy after
ER [34]. Based on the results of the Japan Polyp Study, Matsuda et al. proposed that the
detection of a clean colon in two complete colonoscopies may enable the surveillance
interval to be lengthened to 3 years after polypectomy [35]. According to the latest US guidelines published in 2012, the interval for colonoscopy
after screening and ER is defined based on the characteristics of the resected lesion
[5]. It is desirable to determine an appropriate follow-up period for surveillance colonoscopy
based on risk stratification for the incidence of CRC in Japanese guidelines.
In the present study, the PCCRC rate was 0.3 % during follow-up. Several methods of
calculating PCCRC rates have been published, with reported rates ranging from 2.1 %
to 7.5 % [16]. The present study had a lower PCCRC rate than that reported in previous studies,
and there was no advanced CRC histologically. The possible reasons for this are that
the use of high definition colonoscopy might have enabled us to detect a relatively
larger number of premalignant polyps at the time of initial examination, and that
all colonoscopies were performed by experienced gastroenterologists.
The present study had several limitations. First, it was a retrospective single-institution
study, and some patients were lost to follow-up at other institutions. The number
of patients who underwent the “resect and discard” strategy in 3 years is small because
the procedures were performed only by endoscopists experienced in endoscopic diagnosis
including M-NBI, and the patients who had colorectal lesions equal to or larger than
10 mm were excluded. Second, the present study included endoscopists at a high-volume
center who were familiar with M-NBI, making it difficult to extrapolate the results
to colonoscopists outside of this medical institution. Non-experts should be particularly
cautious when adopting the “resect and discard” strategy in clinical practice. Third,
results for surveillance colonoscopy and CT of the abdomen and pelvis after endoscopic
treatment were not available in more than 30 % of patients. However, the follow-up
rate was about 95 %, and the median follow-up period was more than 6 years. Fourth,
M-NBI is still unpopular in Western countries, as it is generally considered to be
technically difficult and time consuming.
In conclusion, the mid-term outcomes of the “resect and discard” strategy for small
(< 10 mm) colorectal polyps under strict preoperative diagnosis were excellent. The
use of M-NBI following C-WLI can decrease the number of specimens that need to be
sent for histopathological examination, and this could potentially decrease the cost
of colon cancer detection and prevention. Further prospective multicenter studies
involving a larger number of patients with a high rate of follow-up are required to
confirm the present findings.
