Optimal Endoscopic Treatment and Surveillance of Serrated Polyps

Abstract

Serrated polyps are considered precursor lesions that account for 15% to 30% of colorectal cancers, and they are overrepresented as a cause of interval cancers. They are difficult to detect and resect comprehensively; however, recent data suggest that high definition endoscopy, chromoendoscopy (via spray catheter, pump or orally), narrow band imaging, split-dose bowel preparation and a slower withdrawal (>6 minutes) can all improve detection. Cold snare resection is effective and safe for these lesions, including cold snare piecemeal endoscopic mucosal resection, which is likely to become the standard of care for lesions >10 mm in size. Sessile serrated lesions ≥10 mm in size, those exhbiting dysplasia, or traditional serrated adenomas increase the chance of future advanced neoplasia. Thus, a consensus is emerging: a surveillance examination at 3 years should be recommended if these lesions are detected. Serrated lesions likely carry equivalent risk to adenomas, so future guidelines may consider serrated class lesions and adenomas together for risk stratification. Patients with serrated polyposis syndrome should undergo surveillance every 1 to 2 years once the colon is cleared of larger lesions, and their first degree relatives should undergo screening every 5 years starting at age 40.

Full text

Review
Gut and Liver, Published online October 8, 2019
Serrated polyps are considered precursor lesions that ac-
count for 15% to 30% of colorectal cancers, and they are
overrepresented as a cause of interval cancers. They are dif-
ficult to detect and resect comprehensively; however, recent
data suggest that high definition endoscopy, chromoendos-
copy (via spray catheter, pump or orally), narrow band imag-
ing, split-dose bowel preparation and a slower withdrawal
(>6 minutes) can all improve detection. Cold snare resection
is effective and safe for these lesions, including cold snare
piecemeal endoscopic mucosal resection, which is likely to
become the standard of care for lesions >10 mm in size.
Sessile serrated lesions ≥10 mm in size, those exhbiting dys-
plasia, or traditional serrated adenomas increase the chance
of future advanced neoplasia. Thus, a consensus is emerg-
ing: a surveillance examination at 3 years should be recom-
mended if these lesions are detected. Serrated lesions likely
carry equivalent risk to adenomas, so future guidelines may
consider serrated class lesions and adenomas together for
risk stratification. Patients with serrated polyposis syndrome
should undergo surveillance every 1 to 2 years once the co-
lon is cleared of larger lesions, and their first degree relatives
should undergo screening every 5 years starting at age 40.
(Gut Liver, Published online October 8, 2019)
Key Words: Colorectal neoplasms; Serrated polyps; Endo-
scopic mucosal resection; Endoscopic submucosal dissec-
tion; Serrated polyposis syndrome
INTRODUCTION
Colorectal cancer (CRC) is one of the leading causes of mor-
tality around the world. It is the fourth most common cancer
worldwide accounting for 6.1% of total cancers diagnosed
and second leading cause of cancer related death, after lung
cancer, in world.1 In United Kingdom, bowel cancer is the 4th
most common cancer accounting for 12% of all new cancer
diagnosis. Overall, serrated polyps contribute to 20% to 30% of
sporadic CRCs.2 Although serrated lesions are thought to be less
common in Asian populations, a number of studies from Korea
and Hongkong have suggested similar rates to Western co-
horts.3-5 Failure to detect sessile serrated lesions (SSL) is thought
to be one of the reasons for interval CRC6 and the failure of
screening colonoscopy in preventing right sided colon cancers.7
One of the reasons behind this is that SSL are difficult to detect
or visualize during endoscopy due to flat shape and pale or
translucent appearance8 and are often incompletely resected.9
These issues have implications on what should be the optimal
endoscopic treatment and surveillance of serrated polyps which
remains area of active research. Through this review, we attempt
to address this contentious issue through available literature and
evidence.
SESSILE SERRATED POLYPS AND THEIR ENDOSCOPIC
DETECTION
Lesion of the serrated class include sessile serrated polyps
(SSPs) along with hyperplasic polyps and traditional serrated
adenomas form heterogeneous group.10 SSPs can be further
characterized on basis on endoscopic, histological and molecu-
lar features. Endoscopic assessment of SSP is challenging. They
are often subtle, pale in appearance and are frequently masked
by mucous cap.11 Features suggestive of SSL rather than hyper-
plastic polyp include dark spots within pits, indistinct boarder,
a cloud-like or bosselated surface and irregular shape.12,13 Dys-
plastic lesions have transition from flat to nodular, sessile or
depressed area; type III–V pit pattern and NICE 2.14
They are more common in the right side of colon where less
good preparation can make detection challenging. Detection can
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0)
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Optimal Endoscopic Treatment and Surveillance of Serrated Polyps
Vipin Gupta and James E. East
Translational Gastroenterology Unit and Oxford NIHR Biomedical Research Centre, Experimental Medicine Division, Nuffield Department of
Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
Correspondence to: James E East
Translational Gastroenterology Unit and Oxford NIHR Biomedical Research Centre, Experimental Medicine Division, Nuffield Department of Clinical
Medicine, University of Oxford, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK
Tel: +44-1865-228753, Fax: +44-1865-228763, E-mail: james.east@ndm.ox.ac.uk
Received on June 15, 2019. Revised on July 26, 2019. Accepted on August 12, 2019.
pISSN 1976-2283 eISSN 2005-1212 https://doi.org/10.5009/gnl19202

2 Gut and Liver, Published online October 8, 2019
be improved by withdrawing slowly, using high definition colo-
noscope15 and chromoendoscopy (dye spray) (Table 1).16-18 Some
early data suggests the use of Endocuff may support SSL (SSA/
P) detection with a 15% detection rate with Endocuff versus a
3% rate with standard colonoscopy (p=0.001).19 A colonoscope
with a large balloon at the bending section which slows with-
drawal and compresses folds (G-EYE colonoscope; Smart Medi-
cal Systems Ltd., Ra’anana, Israel) also improved serrated lesion
detection rates in a large randomized controlled study (2.7% vs
0.8%, p=0.036).20 A study that looked at narrow-band imaging
(NBI; Olympus, Japan) for serrated polyp detection suggested a
statistical trend toward improved detection with a mean number
of serrated lesions proximal to the sigmoid of 0.51 with NBI
versus 0.39 for white light (p=0.085).21 A subsequent meta-anal-
ysis of NBI for detection of non-adenomatous (serrated) lesions
suggested significantly improved detection with either first or
second generation “Bright” NBI.22 With increasing use of NBI,
the Workgroup on Serrated Polyps and Polyposis (WASP)–has
described classification (also called WASP) for distinguishing
between hyperplastic and adenomatous/serrated polyps (Fig. 1).23
In WASP classification , criterion like “dark spots inside crypt”
are more reliable than criterion “irregular shape.” Also, it does
not incorporate a commonly used criterion in practice, “mucus
cap.”
Although higher bowel preparation quality has previously
not been shown to be associated with improved serrated lesion
detection, a recent meta-analysis suggests that use of split dose
bowel preparation does seem to improve serrated lesion detec-
tion relative risk of 2.48 (95% confidence interval [CI], 1.21 to
5.09).24
ENDOSCOPIC TREATMENT METHODS
The choice of endoscopic resection for any polyp revolves
around two principles; safety and recurrence. Recurrence de-
pends heavily on completeness of endoscopic resection. Size
more than 10 mm and SSP are two strongest predictors of in-
complete endoscopic resection.9 Hence, removal of SSP of size
over 10 mm requires expertise. Cold snare polypectomy is the
preferred method for removal of SSP less than 10 mm. Rela-
tively little data specific to serrated lesions is available; however
in cases series of small polyps which are predominantly adeno-
matous, cold snaring is a very safe and efficacious method and
performs better than cold forceps polypectomy method.25,26 Rates
of complications with cold snare polypectomy are very low and
intra procedural bleeding, 1.8% in one large series, is usually
controlled with injection or endoscopic clipping.17 Perforations
, which are more of concern with hot snare, are exceptionally
rare with cold snare. Majority of the bleed with cold snare are
immediate and self-limiting.
Thin wire (0.30 mm) snares have been shown more effective
than thick wire (0.47 mm) snares in achieving complete endo-
scopic and pathologic excision. Horiuchi
et al.
27 showed, in a
prospective randomized controlled trial of 210 polyps, that thin
wire snares have significantly more complete pathological re-
section as compared to thick wire snare (91% vs 79%, p=0.02).
In another study Din
et al.
28 showed there was significantly
endoscopic complete resection (90.2% vs 73.3%, p<0.05) and
nonsignificant higher trend for complete pathological excision
(73.3% vs 65.2%, p=0.4) with thin wire snares. Injection can be
helpful to help grasp some normal mucosa around the edges of
these flat lesions to maximise chances of comprehensive resec-
tion, and adding methylene blue or indigo carmine to the injec-
tion fluid and provide contrast to see the edges of the lesion
more clearly (Fig. 2).
Table 1. Interventions at Colonoscopy that May Improve Serrated Le-
sion Detection Rates16
Beneficial May be
beneficial No clear benefit
Slower withdrawal >6 min Endocuff Antispasmodics
Chromoendoscopy G-EYE Good vs adequate bowel
High definition Preparation
Narrow-band imaging Wide angle and enhanced
mucosal views
Split dose bowel
preparation
Right colon retroflexion
Fig. 1. Workgroup on Serrated Polyps and Polyposis classification.

Gupta V and East JE: Optimal Endoscopic Treatment and Surveillance of Serrated Polyps 3
ENDOSCOPIC MUCOSAL RESECTION OF LARGE SER-
RATED LESIONS
For lesions greater than 10 mm, endoscopic mucosal resec-
tion (EMR) is the preferred technique. It is important to carefully
inspect larger lesion as they have more chance to have dys-
plasia which may appear as subtle change in surface of polyp
in form of nodularity, elevation or depression with or without
adenomatous pit pattern.29 EMR is safe and efficacious method
of removing larger (>10 mm) SSPs. SSP s are easier to remove
by endoscopic resection as compared to adenomas as they do
not have submucosal fibrosis and are loosely attached to deeper
layers making lifting easy after injection. Rao
et al
.30 showed, in
a large cohort of 251 SSP (>10 mm), EMR could safely remove
polyps with only 3.6% recurrence rate after mean follow-up of
17.8±15.4 months. All recurrences (median size, 4 mm) could be
managed by endoscopic resection.
In a large cohort of laterally spreading tumors (LST) >20 mm,
Pellise
et al
.31 showed EMR could successfully remove SSP as
compared to adenomas with similar adverse events and less
bleeding. The same study showed significantly lower rates of re-
currence with SSP at 6 months (6.3% vs 16.1%) and 12 months
(7.0% vs 20.1%) compared to adenomatous lesions. EMR does
have associated complications which involve bleeding (1/10 to
1/30),32 perforation (1/100) and post polypectomy syndrome
(1/200).33 Given the risks of resection of flat lesion in the right
colon, some authors have suggested that the risks of resection
may outweigh the cancer prevention benefits; however, we
would suggest that cold snare piecemeal EMR (pEMR) is a safe
and effective way to resect these larger right sided serrated le-
sions. Three recent studies have reported cold snare pEMR data,
with or without injection to lift the lesion, with acceptable rates
of recurrence and low complication rates (Table 2), and it seems
likely that cold snare pEMR will become the standard of care for
resection of these lesions in the future.34-36
ENDOSCOPIC SUBMUCOSAL DISSECTION OF LARGE
SERRATED LESIONS
Large SSLs are predominantly right sided, as compared to ad-
enomatous LSTs) which have propensity for being left sided or
rectal. The risk of recurrence in large SSLs is lower than equiva-
lent adenomatous lesions, and the risk of invasive cancer is also
lower for a lesion of equivalent size.30 Endoscopic submucosal
dissection (ESD) has been described in management of large ser-
rated lesion;37 however, it has its own technical challenges, e.g.,
the flap of SSLs is thin and floppy making it difficult to control
using standard gravity-based positioning during ESD. Therefore
the advantages of use of ESD for which are perhaps clearest
for large rectal lesions where the risk of recurrence or invasion
Table 2. Cold Snare Resection of Larger Serrated Lesions
Author (year) No. Size, mm Pathology Complications Recurrence, %
Tate
et al
. (2018)34 34 10–35 SSP None None
Rameshshanker
et al
. (2018)35 29 10–30 SSP None 3.4
Piraka
et al
. (2017)36 94 10–60 75 TA/TVA
19 Serrated
Clip ×19.7
SSP, sessile serrated polyp; TA, tubular adenomas; TVA, tubulo-villous adenoma.
Fig. 2. Cold snare lift and endoscop-
ic mucosal resection of small sessile
serrated lesion. (A) A 5-mm serrated
polyp observed in the ascending
colon. (B) Lesion seen with narrow-
band imaging under magnification;
note the small black dots within the
pits, suggestive of a sessile serrated
lesion. (C) Resected lesion with fluid.
The specimen was stained with
methylene blue as a contrast agent
to clarify the lesion edges. (D) Lesion
grasped with a thin wire cold snare.
Note the additional normal mucosa
snared to ensure complete excision.
(E) Post-resection defect observed
under magnification after washing.
Note that normal mucosa can be
clearly observed around the edges,
confirming excision.

4 Gut and Liver, Published online October 8, 2019
is high, and the consequences of a perforation are lower, are
inverted for serrated lesions which are technically difficult to
resect, occur in the thin walled right colon, and are low risk for
recurrence or invasion.38-40 We therefore recommend cold snare
pEMR for large SSLs, and would only consider ESD for a lesion
assessed as high risk for early sub-mucosal invasion. Traditional
serrated adenomas are morphologically much more similar to
LSTs, are predominantly found in the rectum and may be good
targets for ESD. In a large Korean cohort of SSP/adenoma with
dysplasia/adenocarcinoma, ESD was used as resection method
in 3.8% of patients for SSP ≥20 mm.41
SURVEILLANCE
Due to lack of prospective and controlled data, most of the
recommendations and guidelines are based on expert opinion
and observational data. Table 3 summarizes the current U.S.
Multi-Society Task Force (US MSTF),42 European Society of
Gastrointestinal Endoscopy (ESGE)43 and British Society of Gas-
troenterology (BSG) position statement guidance on surveillance
for serrated polyps (Table 3); however more recently data has
become available both on the comparative risk of small and ad-
vanced serrated lesions versus adenomas and whether serrated
lesions and adenomas should be treated separately or together.
SURVEILLANCE FOR SMALL <10 MM SERRATED LE-
SIONS
The BSG position statement on serrated polyps in the colorec-
tum recommended no surveillance for patients with one or more
serrated lesions <10 mm in size who do not meet the criteria for
serrated polyposis syndrome,16 although US MSTF guidelines
suggests 5 yearly surveillance for 1 to 2 serrated lesions <10
mm in size. There are as yet no prospective data to validate this
recommendation. Schreiner
et al
.44 report in a U.S. cohort from
more than a decade ago, 248 out of 3,121 patients (7.9%) had
at least 1 proximal non-dysplastic serrated polyp (ND-SP). They
were more likely than patients with no proximal ND-SP to have
advanced neoplasia (17.3% vs 10.0%). During surveillance, 39
patients with baseline proximal ND-SP and no neoplasia were
more likely to have neoplasia compared with subjects who did
not have polyps (odds ratio [OR], 3.14). Among patients with
advanced neoplasia at baseline, those with proximal ND-SP
(n=43) were more likely to have advanced neoplasia during
surveillance (OR, 2.17). The United States, pathology based case-
control study suggested that the rate of CRC was significantly
higher in sessile serrated adenomas that in patients with adeno-
mas or hyperplastic polyps over 13 years follow-up (12.5% vs
1.8% vs 1.8%, respectively).45 All serrated lesions with subse-
quent cancer were <10 mm in size; however some SPS patients
and patients with traditional serrated adenomas were included
and it is not clear whether SSAs were resected comprehensively
and not just biopsied. In a large Danish case-control cohort,
which reanalyzed pathological samples using modern defini-
tions of serrated polyps, serrated lesions alone were broadly risk
equivalent to adenomas alone for future cancer risk without
considering size.46 Given that non-advanced serrated lesions ap-
pear risk equivalent to non-advanced adenomas, their surveil-
lance should be equivalent, with no surveillance recommended
by the BSG position statement or ESGE and that patients should
return to population screening.
SURVEILLANCE FOR ADVANCED SERRATED LESIONS
(SSL ≥10 MM, SSL WITH DYSPLASIA OR TRADITIONAL
SERRATED ADENOMA)
The BSG position statement on serrated polyps in the colorec-
tal recommends one off surveillance colonoscopy at 3 years for
patients with an advanced serrated lesion, defined as a SSL ≥10
mm, SSL with dysplasia and traditional serrated adenomas,16 in
line with US MSTF recommendation, and broadly with ESGE
recommendation (Table 3). No prospective data to validate this
recommendation exists; however, a number of lines of evidence
are strongly suggestive that future CRC risk is increased by
these lesions to a level consistent with that post advanced ade-
noma detection. In the Norwegian Colorectal Cancer Prevention
(NORCCAP) screening study, large ≥10mm hyperplastic (ser-
rated) lesions were associated with the same future CRC risk as
advanced adenomas, increased 3- to 4-fold versus no polyps.47
A large Danish cohort which reanalyzed pathological samples
using modern definitions of serrated polyps, traditional serrated
adenomas and SSL with dysplasia had an almost 5-fold higher
Table 3. US MSTF, ESGE and BSG Recommendations for the Surveillance of Sessile Serrated Polyps
Baseline colonoscopy finding Recommended surveillance interval
US MSTF ESGE BSG
Size <10 mm without dysplasia 5 yr 10 yr No surveillance on the basis of serrated polyps
Any lesion ≥10 mm in size or with dysplasia 3 yr 3 yr One off colonoscopy at 3 yr
OR traditional serrated adenoma 3 yr One off colonoscopy at 3 yr
Serrated Polyposis syndrome 1 yr 3 yr genetic counselling 1–2 yr once colon cleared consider genetic counselling
US MSTF, U.S. Multi-Society Task Force; ESGE, European Society of Gastrointestinal Endoscopy; BSG, British Society of Gastroenterology.

Gupta V and East JE: Optimal Endoscopic Treatment and Surveillance of Serrated Polyps 5
risk of future CRC.46
SERRATED POLYPOSIS SYNDROME SURVEILLANCE
Serrated polyposis syndrome (SPS) is common in bowel can-
cer screening programs which use guaiac fecal occult blood
testing (gFOBT) or fecal immunochemical testing (FIT) as a
screening test, with estimates of SPS prevalence ranging from
1:150 to 1:300.48,49 A recent Spanish FIT based cohort followed
up all their patients with proximal serrated polyps, tripling the
number of additional cases of SPS, for a final prevalence of
1:100.50 Therefore, especially when using FIT in bowel cancer
screening, colonoscopists should be alert to a diagnosis of SPS.
US MSTF and ESGE recommend surveillance period of 1 year
and 3 years respectively (Table 3).The BSG position statement
on serrated polyps in the colorectal recommended 1 to 2 yearly
surveillance for patients meeting the World Health Organization
(WHO) criteria for serrated polyposis syndrome.16 This recom-
mendation was on the basis that in early cohorts, future risk of
CRC was elevated at as much as 7% at 5 years;51,52 however in
larger cohorts with rigorous surveillance performed every 1 to
2 years, with all lesions larger than 5 mm in size resected, at
academic centres, the risk appeared much lower with CRC only
diagnosed at 1.9 cases per 1,000 years of patient follow-up.53,54
Recent data suggests once the colon is cleared, follow-up can be
safely deferred to 2 years.54,55
The risk for patient who are first-degree relatives of patients
with SPS also appears elevated between 3- to 5-fold compared
to the general population51,57,58 and screening colonoscopy is
recommended for this group, with subsequent colonoscopies
determined by polyp burden. Surveillance should then be per-
formed every 5 years if no polyps are found.
A recent paper that looked at patients with multiple serrated
polyps and adenomas, not quite meeting the criteria for SPS
also noted that their risk for CRC was equivalent to patients
who met the WHO definition of SPS, and that their first-degree
relatives also had an elevated risk of CRC, comparable to the
risk for first-degree relatives of SPS patients.58
SURVEILLANCE WHEN SERRATED LESIONS AND AD-
ENOMAS ARE FOUND TOGETHER
In previous guidelines it was not possible to comment on
how to assign surveillance intervals when serrated lesions oc-
curred together with adenomas and whether risk, and therefore
surveillance intervals, should be considered separately for each
polyp class or if their risk was additive. At that time, each polyp
class was considered separately and the shortest surveillance
interval was used.16 There has been recent data on the future
risk when adenomas and serrated lesions are found together.
The risk of finding an advanced adenoma at surveillance had an
OR for future risk with synchronous advanced adenomas and
serrated lesions at index exam 4-fold higher than for advanced
adenomas alone. A further similar study from Korea presented
in abstract form suggests additive risk between adenomas and
SSL with the risk of advanced colorectal neoplasia at 3 years
follow-up for adenoma with synchronous serrated polyp being
17.9% versus 10.7% for adenoma alone (p<0.001).59 Audit data
from an Australian CRC surveillance program with 2,157 pa-
tient followed up for a median of 50 months found additive risk
of advanced neoplasia when serrated lesion and adenomas were
found together (high-risk adenoma: hazard ratio [HR]=2.04 [95%
CI, 1.70 to 2.45]; high-risk SSP+adenoma: HR=3.20 [95% CI
1.31 to 7.82]; low-risk SSP+adenoma: HR=2.20 [95% CI, 1.03 to
4.68]).60 Older data from the 1990s when serrated lesions were
less recognised both endoscopically and pathologically is sup-
portive but less definitive.
CONCLUSION
Adequate resection technique and appropriate surveillance
of serrated polyps is of utmost importance as they are a major
reason behind interval cancers and failure of screening colonos-
copy in preventing right sided colon cancers. Their identifica-
tion is difficult and challenging but is aided by increased with-
drawal time and chromoendoscopy. Cold resection techniques
are safe and effective and are increasingly supported by larger
cases series data. Surveillance strategies, on the other hand, are
currently predominantly based on expert opinion and observa-
tional data; however new case series are becoming available to
make these recommendations more evidence based.
CONFLICTS OF INTEREST
No potential conflict of interest relevant to this article was
reported.
ACKNOWLEDGEMENTS
J.E.E. was funded by the National Institute for Health Re-
search (NIHR) Oxford Biomedical Research Centre (BRC). The
views expressed are those of the author(s) and not necessarily
those of the NHS, the NIHR or the Department of Health.
ORCID
Vipin Gupta https://orcid.org/0000-0002-9620-1696
James E. East https://orcid.org/0000-0001-8035-3700
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