Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_850_Библиотеки_им_академика_М_И_Перельмана
.pdf
12 COLORECTAL CANCER 185
https://t.me/medicina_free
• Rectal retroversion rate – the percentage of procedures in
which the endoscope is inverted in the rectum to visualize the
anorectal margin
• Colonoscope withdrawal time – the amount of time the endoscopist takes to withdraw the colonoscopy while observing the
colonic mucosa
• Use of sedation – a safety measure of sedation dosing in different age groups to ensure sedation is used safely
• Number of colonoscopy procedures undertaken per annum
• Comfort during colonoscopy – a five-point scale in which
the comfort of the patient during a consciously sedated colonoscopy is assessed
• Perforation rate – the rate at which a perforation occurs during a diagnostic colonoscopy
The proportions used in these metrics vary between international endoscopic regulatory bodies, however the factors measured are uniform. Regular audit of these metrics allows
identification of individual endoscopists who may require
additional targeted training and allows minimization of risk to
patients attending for colonoscopy.
Premalignant Lesions of the
Colon Mucosa
There are several main types of lesions that can develop in the
colon, each with its own characteristic endoscopic appearance
and differing risks of malignant progression.
the crypts are star-shaped on cross-section. Hyperplastic
polyps are often found in the sigmoid colon and rectum and are
thought to have no malignant potential. Hyperplastic polyps
are quite common, with a prevalence around 20% (Hazewinkel
etal. 2014; Kim etal. 2014).
Sessile Serrated Lesions
Similar to a hyperplastic polyp, a sessile serrated lesion also has
serrated crypts, but in contrast to the hyperplastic polyp a sessile serrated lesion also has architectural disturbances at the
crypt base. On histological examination the crypt base is widened with a basal horizontal extension, giving the appearance
of a L or inverted T-shaped crypt base.
Endoscopically, sessile serrated lesions can be found throughout
the colon but especially in the right side of the colon and often
present as flat or slightly elevated pale lesions that are easily
missed. Sessile serrated lesions do carry a risk of malignant progression and it is estimated that at least 10% of all sporadic colon
cancers derive from sessile serrated lesions (García-Solano etal.
2010; Mäkinen etal. 2001). The molecular sequence of malignant
progression is distinct from the adenoma-carcinoma sequence
and involves mutations in KRAS and BRAF and widespread CpG
island methylation and microsatellite instability. The prevalence
of sessile serrated lesions is around 5% (Hazewinkel etal. 2014;
Kim etal. 2014).
Traditional Serrated Adenoma
Adenomas
An adenoma is a focal lesion defined by the presence of a
degree of dysplasia (at least low-grade dysplasia). Adenomas
are a well-recognized precursor lesion of colorectal cancer
though the adenoma–carcinoma pathway that is driven by
mutations in the APC, KRAS, and TP53 genes and dysregulation of the transforming growth factor β (TGFβ) signaling
pathway. As the adenoma acquires progressive mutations, this
leads to increased proliferation and eventually invasive malignancy (Fearon and Vogelstein 1990; Smit etal. 2020). Adenomas
can present in many different shapes, including flat, sessile and
pedunculated. The risk of malignancy is increased with
increasing size, an ulcerated depression in part of the lesion
and a disorganized or absent vascular pattern seen on either
white light or with enhanced endoscopic imaging techniques.
The incidence of adenoma increases with age. It is estimated to
be around 20–30% in large cohorts of asymptomatic patient
undergoing colonoscopy (Ferlitsch etal. 2011; Kim etal. 2014).
Hyperplastic Polyps
Hyperplastic polyps are bland and usually diminutive lesions.
In contrast to an adenoma a hyperplastic polyp never contains
any degree of dysplasia. Histologically the luminal side of the
hyperplastic crypts has a serrated (saw-tooth) appearance and
Traditional serrated adenomas are characterized by the
presence of serrated crypts, prominent eosinophilic cytoplasm
and ectopic crypts. Traditional serrated adenomas are most
often found in the sigmoid colon and rectum and endoscopically present as pedunculated or sessile lesions. They are often
KRAS and BRAF mutated but, unlike sessile serrated lesions,
often lack microsatellite instability. Traditional serrated adenomas are rare with a prevalence of less than 1% (Hazewinkel
etal. 2014; Kim etal. 2014) Dysplasia has been described in
traditional serrated adenomas (Kim etal. 2010) but the risk of
malignant progression is currently unclear, possibly reflecting
their low incidence.
Classication Systems
Multiple classification systems for premalignant colonic lesions
have been developed. They allow for a standardized description
of lesions encountered and also provide information on the
malignant potential and the risk of deep invasion.
Paris Classification
The Paris system is used to classify superficial lesions of the
gastrointestinal tract based on their shape (Participants in the
Paris Workshop 2003). Lesions are best observed using white
light. Somewhat confusing, all lesions in the Paris classification
186 2 COLORECTAL AND ANAL CANCER
https://t.me/medicina_free
are type 0 lesions; this is because the Paris classification was an
extension of a previous classification for advanced gastric cancers (the Borrmann classification, that grades lesions from type
1 to type 4). The type 0 classification was added to describe
superficial lesions and has the following subdivisions:
• Type 0-I (polypoid lesions) which includes the subtype 0-Ip
for pedunculated and 0-Is for sessile lesions.
• Type 0-II (non-polypoid) which included the subtype 0-IIa
for slightly elevated, 0-IIb for flat and-IIc for slightly depressed
lesions.
• Type 0-III that described excavated lesions with an ulcerative
appearance and suggests submucosal invasion.
Some lesions are best described by a combination of Paris
classifications; for example, a slightly elevated lesion with a
central depression can be describes as type 0-IIa+IIc.
The Paris classification can be used to estimate submucosal
invasion, the change of which is increased in type 0-IIc and in
particular in type 0-III lesions.
NICE Classification
The NBI International Colorectal Endoscopic (NICE)
classification system uses NBI to classify lesions (Hewett etal.
2012). It looks at the color of the lesion, vessels and surface
pattern to classify lesions in one of three categories:
• Type 1: color same or lighter than background, none or isolated lacy vessels, and a surface pattern of uniform white or
dark spots suggests a hyperplastic lesion
• Type 2: color darker than background, brown vessels surrounding white structures and a surface pattern of oval, tubular
or branched white structures suggests an adenoma
• Type 3: color darker than background with sometimes
patchy white areas, disorganized or missing vessels, and an
amorphous or absent surface pattern suggests a submucosal
invasion.
While the Paris and NICE classification are the most commonly used in the western world, there are a number of other
classification system that use NBI imaging that look at microvessel pattern (SANO, Jikei), surface pattern (Showa) or a
combination of both (Hiroshima, JNET). These classification systems were all developed in Japan and are commonly used in Asia.
WASP Classification
Most classification systems do not allow differentiation between hyperplastic polyps and sessile serrated lesions. The
increasing recognition that these two lesions are biologically
distinct entities led to the development of the Workgroup serrAted polypS and Polyposis (WASP) classification (Jeg etal.
2016). It identifies four characteristics to identify sessile serrated polyps under narrow band imaging: a clouded surface,
indistinct border, irregular shape and dark spots inside crypts.
The presence of at least two criteria is sufficient to label a lesion
a sessile serrated polyp.
Resection of Colorectal Lesions
Endoscopic resection of colorectal lesions provides a spectrum
of complexity from simple snare resection of small lesions
through to complex resection techniques allowing very large
premalignant lesions to be removed. Advanced resection techniques are a subspecialty within the field of endoscopy and
referral to an appropriately trained endoscopist is essential in
providing the best outcome in terms of complete resection and
reduced risk of complications. It is currently practice to remove
the vast majority of any detected polypoid lesion of the colon at
colonoscopy, and as the most commonly found are small lesions
all colonoscopists are trained to undertake resection of these.
Snare Polypectomy
The majority of colorectal polyps can be resected at the index
colonoscopy using snare polypectomy. A wire loop is placed
over the lesion and closed around it. The lesion is then either
removed using a cold snare technique in which the wire of the
snare is designed to cut through mucosal tissue or using an
electrosurgical diathermy machine to provide coagulation of
any vasculature supplying the lesion – known as a “hot snare”.
Typically, a small sessile lesion less than 6 mm in size (Paris
Classification 0-Is or 0-IIa, b or c) will be removed with a cold
snare technique while pedunculated lesions using a hot snare.
Endoscopic Mucosal Resection (EMR)
EMR was first described in 1973 using a hypertonic saline solution to provide separation of the mucosal and muscularis tissue
planes to allow dissection of a lesion (Deyhle etal. 1973). The
technique is now a standard practice for colonoscopists to
ensure safe resection of sessile lesions greater than 1 cm in size.
The technique involves a needle injector device through the
working channel of the colonoscope to lift the lesion away from
the muscularis. The injected solution can vary, but is usually a
combination of adrenaline, colloid and a blue stain such as
methylene blue or indigocarmine dye. This solution temporarily colors the underlying muscularis blue to allow the endoscopist to visualize that the resection margin is adequate and
that the wall of the colon is intact. Lifting the lesion to be
resected away from the underlying muscle using the injected
solution reduces the risk of perforation.
Once a lesion is adequately lifted, a snare device is placed
around the lesion and combined electrosurgical current of
coagulation and cutting is used to remove it. Larger lesions are
removed piecemeal, with sections removed piece by piece until
the resection is completed. For the resection of flat colorectal
https://t.me/medicina_free
lesions, the utilization of cold snare EMR appears to be as effective as using electrosurgical snaring at complete resection,
while reducing the risk of perforation and having similar risk of
bleeding. Figure 1 demonstrates a large laterally spreading
tumor of the ascending colon, lifted and removed with EMR.
Following EMR a number of techniques have been examined
in the literature including coagulation of the margin with either
argon plasma coagulation or using diathermy application via
the tip of a snare (Katsinelos et al. 2019; Kemper etal. 2021;
Motchum etal. 2022). It is not definitively clear whether these
techniques provide any advantage over endoscopically assessing complete resection combined with snare resection of
remaining margins of adenoma.
The risks of EMR are bleeding, perforation and incomplete
resection. The risk of bleeding is around 3% and depends on
lesion size, patient comorbidity and use of anticoagulation (De
Ceglie et al. 2016; Ferlitsch et al. 2017). Perforation risk is
around 1% (De Ceglie etal. 2016; Heldwein etal. 2005). The
risk of incomplete resection increases with lesion size and use
of piecemeal resection.
12 COLORECTAL CANCER 187
Endoscopic Submucosal Dissection (ESD)
ESD allows the “en-bloc” resection of lesions. The technique
requires advanced training and is carried out in a limited
number of centers internationally. The lesion is lifted in a similar manner to an EMR, however rather than utilizing snare
resection, a specially designed electrosurgical knife is used to
dissect between the lesion and submucosal plane. The lesion is
then removed as a single surgical sample. The technique has a
slightly higher bleeding risk (1–2%) and increased perforation
risk (5–8%) compared with EMR (De Ceglie etal. 2016; Hong
etal. 2016; Lee etal. 2013; Okamoto etal. 2017) but for large
lesions the risk of recurrence is lower. The procedure also takes
significantly longer to perform than an EMR.
EMR and ESD techniques complement each other, however
limitations in the number of centers providing ESD is currently
prohibitive in offering it to all patients.
Full Thickness Resection (FTR)
The endoscopic FTR technique is relatively new technology,
emerging in 2014. This allows a lesion to be resected by
removing the entire thickness of the colon or rectum. The
lesion is marked around the margin using a diathermy marker
and is then pulled into a cap which has a clip and a snare fitted
to it. The clip is then deployed and the snare cuts through the
tissue pulled into the cap. This technique has evidence emerging that it can be utilised in the removal of early T1 colorectal
cancers and for the completion of polypectomy in which scarring following EMR or ESD means that these techniques are
unable to provide endoscopic resection of remnant adenomatous tissue.
Figure 1 (A) Laterally spreading tumor of the ascending colon. (B) Lifting
solution applied. (C) Resection site of the lesion with muscle stained blue.
188 2 COLORECTAL AND ANAL CANCER
https://t.me/medicina_free
Endoscopic Stenting of Colorectal
Lesions
The rate of large bowel obstruction due to colon cancer is estimated to be around 8% – 13% of all patients with colorectal
cancer (Cheynel etal. 2007; Jullumstrø etal. 2011; Winner etal.
2013). Historically, emergency surgical interventions (resection or the creation of a decompression stoma) have been the
standard approach for patients with a malignant obstruction of
the colon. However, in the last decades endoscopic stenting has
emerged as an alternative to emergency surgery.
A colonic stent is a self-expanding nickel-titanium alloy
cylinder that may be covered with a plastic outer layer or be
bare metal (often termed covered and uncovered metal stents).
The malignant stricture is approached with the colonoscope
and guidewire is passed through it followed by a catheter, using
radiological screening. An injection of contrast proximal to the
stricture confirms the guidewire is correctly located and the
stent is then placed across the guidewire and deployed. The
main risk of colorectal stent placement is perforation of the
malignant lesion, however there is no difference in mortality
for patients presenting with obstruction managed surgically or
with endoscopic stenting (Veld etal. 2020). Figure 2 demonstrates a colorectal stent after endoscopic placement.
Endoscopic Surveillance of Benign and
Malignant Colorectal Pathology
The surveillance of colorectal lesions will vary internationally,
however the principles are the same throughout. Patients presenting with benign colorectal lesions such as adenomas and sessile
serrated lesions can be risk stratified based on the number and
size of the lesions detected at the index colonoscopy. Following
this stratification, a surveillance pathway is followed to ensure
risk reduction for developing colorectal cancer in the future.
In the United Kingdom, the stratification is based on the index
colonoscopy being of high quality, and a repeat colonoscopy
is recommended in the case of either poor bowel preparation
or incomplete colonoscopy. Provided the index colonoscopy is
completed to a satisfactory standard the stratification is made
into high risk or low risk. Low risk patients are not offered any
surveillance colonoscopy, however the guidance does allow for
clinical judgement to be applied to younger patients falling into
a low risk category. High risk patients are those with either 5
or more adenomas or 2 or more adenomas where 1 is greater
than 10
mm in size. The high risk group are offered a colonoscopy in 3 years and the risk stratification is applied again at this
appointment (Rutter etal. 2020).
If at the index colonoscopy a large lesion requiring advanced
resection such as EMR or ESD is detected, then after resection
a site check is performed between 2 and 6 months following
resection. After this, a one-year surveillance colonoscopy and
then a three-year surveillance colonoscopy are performed. At
the three-year surveillance colonoscopy the risk stratification is
applied again. For patients with colorectal cancer a surveillance
is offered at 1 year and then 3 years, unless there was an impassable cancer in which case colonoscopy is offered as soon as is
considered safe (usually around 3 months) following surgical
resection.
Conclusion
Endoscopic techniques for the detection, assessment and resection of colorectal neoplastic pathology have developed over the
past 30 years to allow non-surgical management of such lesions.
This has allowed reductions in the risk to patients in treating
Figure 2 Endoscopically inserted self-expanding stent.
12 COLORECTAL CANCER 189
https://t.me/medicina_free
these lesions by moving them from surgical treatment pathways into endoscopic treatment.
Key Points of Current Management
1 Colonoscopy is the gold standard in the diagnosis of colorectal neoplastic pathology.
2
Quality in colonoscopy is the single most important factor
in ensuring that colorectal cancers are detected at the index
procedure.
Endoscopic imaging technology has improved with enhanced
3
resolution, image manipulation and artificial intelligence to help
the endoscopist in making a diagnosis.
4
Endoscopic resection techniques now provide safe and effec-
tive management of large colorectal benign lesions and often
allow patients to avoid surgical resections.
Endoscopic stenting of colorectal lesions is a potential treatment
5
option in patients presenting with large bowel obstruction due to
colorectal cancer.
Areas for Further Research
1 How will artificial intelligence in colonoscopy assist endoscopists in the reduction of post colonoscopy colorectal cancer?
2
What techniques at the time of EMR will reduce the risk of
adenoma recurrence?
3 For circumferential colorectal lesions not suitable for surgical intervention, what is the best timing for placement of a
colorectal stent?
Trusted Links for Further Reading
Key performance indicators for colonoscopy: Rees CJ, Thomas
Gibson S, Rutter MD, Baragwanath P, Pullan R, Feeney M, e.a.
UK key performance indicators and quality assurance standards for colonoscopy. Gut. Dec 2016;65(12):1923–9. https://
www.bsg.org.uk/clinical-resource/uk-key-performance-indicators-and-quality-assurance-standards-for-colonoscopy
How to Manage Large Colorectal Polyps EMR vs. ESD.
UEGWeek2012_Syllabus_121002.indd
Crockett SD, Nagtegaal ID. Terminology, Molecular Features,
Epidemiology, and Management of Serrated Colorectal Neoplasia.
Gastroenterology. Oct 2019;157(4):949–966.e4. https://www.gastrojournal.org/article/S0016-5085(19)41115–3/fulltext
References
Atkinson, N.S.S., Ket, S., Bassett, P. etal. (2019 Aug). Narrow-band imaging
for detection of neoplasia at colonoscopy: a meta-analysis of data from
individual patients in randomized controlled trials. Gastroenterology
157 (2): 462–471.
Brown, S.R., Baraza, W., Din, S., and Riley, S. (2016 Apr). Chromoscopy
versus conventional endoscopy for the detection of polyps in the colon
and rectum. Cochrane Database Syst Rev 7 (4): CD006439.
Cheynel, N., Cortet, M., Lepage, C. etal. (2007 Oct). Trends in frequency
and management of obstructing colorectal cancers in a well-defined
population. Dis Colon Rectum 50 (10): 1568–1575.
De Ceglie, A., Hassan, C., Mangiavillano, B. etal. (2016 Aug). Endoscopic
mucosal resection and endoscopic submucosal dissection for colorectal
lesions: a systematic review. Crit Rev Oncol Hematol 104: 138–155.
Deyhle, P., Largiadèr, F., Jenny, S., and Fumagalli, I. (1973 Feb). A method for
endoscopic electroresection of sessile colonic polyps. Endoscopy 5 (1): 38–40.
Fearon, E.R. and Vogelstein, B. (1990 Jun 1). A genetic model for colorectal
tumorigenesis. Cell 61 (5): 759–767.
Ferlitsch, M., Moss, A., Hassan, C. etal. (2017 Mar). Colorectal polypectomy
and endoscopic mucosal resection (EMR): European Society of
Gastrointestinal Endoscopy (ESGE) clinical guideline. Endoscopy 49 (3):
270–297.
Ferlitsch, M., Reinhart, K., Pramhas, S. et al. (2011 Sep 28). Sex-specific
prevalence of adenomas, advanced adenomas, and colorectal cancer in
individuals undergoing screening colonoscopy. JAMA 306 (12): 1352–1358.
Froehlich, F., Wietlisbach, V., Gonvers, J.J. etal. (2005 Mar). Impact of colonic
cleansing on quality and diagnostic yield of colonoscopy: the European
Panel of Appropriateness of Gastrointestinal Endoscopy European
multicenter study. Gastrointest Endosc 61 (3): 378–384.
García-Solano, J., Pérez-Guillermo, M., Conesa-Zamora, P. etal. (2010 Oct).
Clinicopathologic study of 85 colorectal serrated adenocarcinomas:
further insights into the full recognition of a new subset of colorectal
carcinoma. Hum Pathol 41 (10): 1359–1368.
Gong, D., Wu, L., Zhang, J. etal. (2020 Apr). Detection of colorectal adenomas
with a real-time computer-aided system (ENDOANGEL): a randomized
controlled study. Lancet Gastroenterol Hepatol 5 (4): 352–361.
Hazewinkel, Y., de Wijkerslooth, T.R., Stoop, E.M. et al. (2014 Mar).
Prevalence of serrated polyps and association with synchronous advanced
neoplasia in screening colonoscopy. Endoscopy 46 (3): 219–224.
Heldwein, W., Dollhopf, M., Rösch, T. et al. (2005 Nov). The Munich
Polypectomy Study (MUPS): prospective analysis of complications and
risk factors in 4000 colonic snare polypectomies. Endoscopy 37 (11):
1116–1122.
Hewett, D.G., Kaltenbach, T., Sano, Y. etal. (2012 Sep). Validation of a simple
classification system for endoscopic diagnosis of small colorectal polyps
using narrow-band imaging. Gastroenterology 143 (3): 599–607.e1.
Hong, S.N., Byeon, J.S., Lee, B.I. et al. (2016 Jul). Prediction model and
risk score for perforation in patients undergoing colorectal endoscopic
submucosal dissection. Gastrointest Endosc 84 (1): 98–108.
Jeg, I., Bastiaansen, B.A.J., van Leerdam, M.E. etal. (2016 Jun). Development
and validation of the WASP classification system for optical diagnosis of
adenomas, hyperplastic polyps and sessile serrated adenomas/polyps.
Gut 65 (6): 963–970.
Jullumstrø, E., Wibe, A., Lydersen, S., and Edna, T.H. (2011 May). Colon
cancer incidence, presentation, treatment and outcomes over 25 years.
Colorectal Dis 13 (5): 512–518.
Katsinelos, P., Lazaraki, G., Chatzimavroudis, G. etal. (2019). A retrospective
comparative study of argon plasma versus polypectome snare tip
coagulation: effect on recurrence rate after resection of large laterally
spreading type lesions. Ann Gastroenterol 32 (2): 178–184.
Kemper, G., Turan, A.S., Schoon, E.J. et al. (2021 Oct). Endoscopic
techniques to reduce recurrence rates after colorectal EMR: systematic
review and meta-analysis. Surg Endosc 35 (10): 5422–5429.
Kim, H.Y., Kim, S.M., Seo, J.H. etal. (2014 Apr 28). Age-specific prevalence
of serrated lesions and their subtypes by screening colonoscopy: a
retrospective study. BMC Gastroenterol 14: 82.
190 2 COLORECTAL AND ANAL CANCER
https://t.me/medicina_free
Kim, K.M., Lee, E.J., Kim, Y.H. et al. (2010 May). KRAS mutations
in traditional serrated adenomas from Korea herald an aggressive
phenotype. Am J Surg Pathol 34 (5): 667–675.
Lee, C.K., Lee, S.H., and Hwangbo, Y. (2011 Sep). Narrow-band imaging
versus I-Scan for the real-time histological prediction of diminutive
colonic polyps: a prospective comparative study by using the simple
unified endoscopic classification. Gastrointest Endosc 74 (3): 603–609.
Lee, E.J., Lee, J.B., Lee, S.H. et al. (2013 Jan). Endoscopic submucosal
dissection for colorectal tumors–1,000 colorectal ESD cases: one
specialized institute’s experiences. Surg Endosc 27 (1): 31–39.
Mäkinen, M.J., George, S.M., Jernvall, P. et al. (2001 Mar). Colorectal
carcinoma associated with serrated adenoma–prevalence, histological
features, and prognosis. J Pathol 193 (3): 286–294.
McGill, S.K., Evangelou, E., Ioannidis, J.P.A. etal. (2013 Dec). Narrow band
imaging to differentiate neoplastic and non-neoplastic colorectal polyps
in real time: a meta-analysis of diagnostic operating characteristics. Gut
62 (12): 1704–1713.
Motchum, L., Levenick, J.M., Djinbachian, R. et al. (2022 Jun 17).
Endoscopic mucosal resection combined with hybrid argon plasma
coagulation to prevent recurrence of large nonpedunculated colorectal
polyps. Gastrointest Endosc 96 (5): 840–848.e2. S0016-5107(22)01769-2.
Okamoto, K., Watanabe, T., Komeda, Y. et al. (2017). Risk Factors for
Postoperative Bleeding in Endoscopic Submucosal Dissection of
Colorectal Tumors. Oncology 93 (Suppl 1): 35–42.
Participants in the Paris Workshop. (2003 Dec). The Paris endoscopic
classification of superficial neoplastic lesions: esophagus, stomach, and colon:
November 30 to December 1, 2002. Gastrointest Endosc 58 (6 Suppl): S3–43.
Rees, C.J., Rajasekhar, P.T., Wilson, A. et al. (2017 May). Narrow band
imaging optical diagnosis of small colorectal polyps in routine
clinical practice: the Detect Inspect Characterise Resect and Discard 2
(DISCARD 2) study. Gut 66 (5): 887–895.
Rees, C.J., Thomas Gibson, S., Rutter, M.D. etal. (2016 Dec). UK key
performance indicators and quality assurance standards for colonoscopy.
Gut 65 (12): 1923–1929.
Repici, A., Badalamenti, M., Maselli, R. etal. (2020 Aug). Efficacy of real-
time computer-aided detection of colorectal neoplasia in a randomized
trial. Gastroenterology 159 (2): 512–520.e7.
Rutter, M.D., East, J., Rees, C.J. etal. (2020 Feb 1). British Society of
Gastroenterology/Association of Coloproctology of Great Britain and
Ireland/Public Health England post-polypectomy and post-colorectal
cancer resection surveillance guidelines. Gut 69 (2): 201–223.
Smit, W.L., Spaan, C.N., Johannes de Boer, R. etal. (2020 Oct 13). Driver
mutations of the adenoma-carcinoma sequence govern the intestinal
epithelial global translational capacity. Proc Natl Acad Sci U S A 117 (41):
25560–25570.
Spadaccini, M., Iannone, A., Maselli, R. etal. (2021 Oct). Computer-aided
detection versus advanced imaging for detection of colorectal neoplasia:
a systematic review and network meta-analysis. Lancet Gastroenterol
Hepatol 6 (10): 793–802.
Subramanian, V., Mannath, J., Hawkey, C.J., and Ragunath, K. (2011 Jun).
High definition colonoscopy vs. standard video endoscopy for the
detection of colonic polyps: a meta-analysis. Endoscopy 43 (6): 499–505.
Veld, J.V., Amelung, F.J., Borstlap, W.A.A. etal. (2020 Mar 1). Comparison
of decompressing stoma vs stent as a bridge to surgery for left-sided
obstructive colon cancer. JAMA Surg 155 (3): 206–215.
Wang, P., Liu, X., Berzin, T.M. etal. (2020 Apr). Effect of a deep-learning
computer-aided detection system on adenoma detection during
colonoscopy (CADe-DB trial): a double-blind randomised study. Lancet
Gastroenterol Hepatol 5 (4): 343–351.
Winner, M., Mooney, S.J., Hershman, D.L. etal. (2013 Aug). Incidence and
predictors of bowel obstruction in elderly patients with stage IV colon
cancer: a population-based cohort study. JAMA Surg 148 (8): 715–722.
Imaging and Staging of
Colorectal Cancer
Jeremy Meyer, David Bowden & Justin Davies
Introduction
The treatment of colorectal cancer is almost invariably surgical,
involving the removal of the primary lesion and, if possible and
indicated, the removal of metastatic (secondary) lesions. The
only exception to this paradigm is represented by patients for
whom a “watch and wait” strategy has been adopted after
complete clinical response following neoadjuvant treatment for
rectal cancer. The prognosis of colorectal cancer has improved
over the last decades, notably following the introduction of
total mesorectal excision (TME) for rectal cancer and of neoadjuvant treatment for preoperative downstaging rectal cancer.
The indication for neoadjuvant treatment is historically based
on the stage of the tumor and its relation to adjacent anatomical
structures, adequate pre-operative staging by modern imaging
techniques being key for optimal surgical and oncological
planning. However, more recent guidelines from the National
Institute for Health and Care Excellence (NICE) in the United
Kingdom recommend neoadjuvant treatment for all patients
with rectal cancer (NIfHaCE 2020), although this has been met
with some challenge (Davies etal. 2022). Further, identifying
patients with locally advanced cancer who will require multidisciplinary surgical input, or those with metastatic disease, is
mostly the remit of expert gastrointestinal radiologists working
within multidisciplinary teams.
The objectives of imaging for colorectal cancer are therefore
multiple. The first objective of imaging is to identify and stage
the primary lesion, in terms of local extension but also in terms
of potentially metastatic lymph nodes, in order to assess surgical
resectability and to decide on the surgical procedure required
and the possible need for multivisceral or en bloc resection to
achieve clear resection margins. In patients with rectal cancer,
resectability can be reassessed after neo-adjuvant treatment.
The second objective is to check for the presence of potentially
distant metastases, either in central lymph nodes not accessible
to conventional surgery, in other organs or in the peritoneal
cavity. Finally, the third objective is to rule out the presence of a
synchronous lesion in the gastrointestinal tract, especially in
patients with a genetic predisposition to colorectal cancer.
12 COLORECTAL CANCER 191
https://t.me/medicina_free
Colon Cancer
Recommended Imaging
The minimum required imaging for colon cancer consists of a
CT of the abdomen and pelvis to characterize the primary cancer
and its relation to anatomical structures (cT stage), the eventual
presence of enlarged lymph nodes (cN stage) and the eventual
presence of distant metastases (cM stage), associated with a CT
of the chest to look for lung metastases. The liver, an organ at risk
for colorectal cancer metastases due to its filtering function of
the portal blood flow, is assessed by the abdominal CT with, in
case of doubt, a dedicated Primovist contrast liver MRI. The
presence of a synchronous cancer in the colon is assessed using a
complete colonoscopy in an adequately prepared patient or, if
colonoscopy cannot be performed, a CT colonography. In case
the recommended imaging cannot be performed before the
removal of the primary lesion, which can be the case – for
example – in a patient with an obstructing sigmoid cancer, the
examinations to rule out metastatic disease and synchronous
cancer should be performed when the clinical situation allows,
but ideally within three months (Argiles etal. 2020).
Classication System
The classification of the primary cancer and its eventual
secondary lesions relies on the latest version of the Union for
International Cancer Control (UICC) TNM system (Table 1).
However, as this classification is – in the context of preoperative imaging – provisional, it is usually preceded by a “c”
(meaning “clinical”). For instance, if lymph nodes are enlarged
on the preoperative CT, the provisional stage will indicate cN+
(or cN1 or cN2), but only the definitive histopathological analysis of the operative specimen will indicate if these lymph
nodes contain metastatic cells (pN+) or not (pN0).
Assessing the Primary Lesion (T)
The gold standard for assessing the primary colon cancer lesion
and its local extension is a CT of the abdomen and pelvis. The
classical features of colorectal cancer on CT are usually either as
a soft tissue mass or bowel wall thickening that may be associated with luminal narrowing (“apple core” appearance). The
mass will typically enhance in a similar fashion to the bowel
wall, though large lesions may undergo central necrosis.
Texture analysis may help differentiating benign thickening of
the bowel wall from colorectal cancer (Wang etal. 2020). Up to
41% of patients suffering from colorectal cancer are first diagnosed in the emergency setting (Bass etal. 2009). Therefore,
large bowel obstruction or lower gastrointestinal bleeding
should raise the suspicion of cancer, which should be investigated by colonoscopy.
If the colorectal cancer can be visualized by CT, this helps in
defining its location, which is often less accurate when assessed
by colonoscopy. The gold standard for localizing the tumor
remains, however, surgical exploration and visualizing the
distal tattoos placed by the endoscopist.
CT has moderate reliability for defining the T stage, which is
correctly predicted in only 60% of patients (Smith etal. 2007)
(Figure 1). The diagnostic accuracy of CT is lowest for early
colorectal cancer, for which endoscopic ultrasound is better,
although the clinical significance of accurately staging early
Table 1 TNM classification of colon and rectal cancer, adapted from the AJCC Cancer Staging Manual (8th Edition).
T stage T1 Invasion of the submucosa by the primary tumor
T2 Invasion of the muscularis propria by the primary tumor
T3 Invasion of the subserosa by the primary tumor
T4 Invasion of other organs/structures and/or the visceral peritoneum by the primary tumor
T4a Invasion of the visceral peritoneum by the primary tumor
T4b Invasion of nearby organs by the primary tumor
N stage N0 No metastasis in regional lymph nodes
N1 1–3 metastatic regional lymph node(s)
N1a 1 metastatic regional lymph node
N1b 2–3 metastatic regional lymph nodes
N1c No metastasis in regional lymph nodes but satellite cancer cells in the non-peritonealized tissues near the tumor
N2 >3 metastatic regional lymph nodes
N2a 4–6 metastatic regional lymph nodes
N2b >6 metastatic regional lymph nodes
M stage M0 No distant metastasis
M1 Distant metastasis(es)
M1a 1 distant metastasis
M1b >1 distant metastasis
M1c Metastasis to the peritoneum (peritoneal carcinomatosis) with or without other organ(s)
192 2 COLORECTAL AND ANAL CANCER
https://t.me/medicina_free
Figure 1 Axial (A) and coronal multiplanar reformat (MPR, (B)) image of a T2/3 sigmoid tumor (arrow). Resolution of CT is inadequate to reliably
differentiate early stages of colorectal tumors given its inability to resolve bowel wall layers and differentiate T2 from T3 disease. Identification of T4a from
T3 disease may also be challenging in the presence of benign desmoplastic change (not shown).
Figure 2 (A) Coronal multiplanar reformatted images of an apple core lesion of the hepatic flexure in a patient with colonic pseudo-obstruction.
(B) Endoluminal virtual colonoscopic image of the tumor, generated from the same image data made possible by surrounding gaseous distension of the bowel.
colonic cancer by CT is of limited importance. CT is better for
more advanced T stages. For instance, the sensitivity and specificity of CT to detect tumor invasion beyond the muscular
propria are 86% and 78% respectively (Dighe etal. 2010). Of
note, the presence of colon wall deformity, notably an apple
core appearance, is highly predictive of stage T3 disease or
higher (Flor etal. 2013) (Figure 2).
Distinguishing T3 from T4 disease is sometimes not possible, as identifying early progression into the peritoneum
cannot be reliably made by CT. The involvement of other
12 COLORECTAL CANCER 193
https://t.me/medicina_free
Figure 3 (A, C) Axial CT and (B, D) Axial T2-weighted MR image at corresponding levels of a large T4b sigmoid tumor (asterisk) involving the left
common iliac artery (open arrow), transversalis fascia (dashed arrow) and adjacent small bowel loops (solid white arrows). Given the superior resolution of
MRI its use is invaluable where there may be uncertainty regarding early adjacent organ invasion.
organs by direct tumor invasion is usually suggested by loss of
the fat plane accompanied by spicular projections or more
obvious invasion. Identification of T4 disease is of importance,
as it may change the therapeutic management, both in terms of
potential neo-adjuvant treatment (Body et al. 2021) and in
terms of surgical strategy (Figure 3). It should be mentioned
that CT has moderate sensitivity for assessing involvement of
the retroperitoneal surgical margin (Elibol etal. 2016).
Preoperative CT with arterial and portal venous phase
imaging also aids in the surgical planning where precise
knowledge of the vascular anatomy and its variations (Alsabilah
et al. 2017; Kuzu et al. 2017) is of importance, such as, for
example, in patients who may be considered for complete
mesocolic excision during which significant vascular complications are a risk.
for colorectal cancer numbers lymph node stations according
to their anatomical locations (Japanese Society for Cancer of
the C, Rectum 2019). The lymph node drainage of colorectal
cancer follows the vascular axis feeding the tumor, and therefore potential metastatic lymph nodes should be expected
along these axes. In right colon cancer, metastatic lymph nodes
are found in 41.5% of patients. D2 lymph nodes contain metastatic deposits in 9.7% of patients, and D3 lymph nodes in 1.5%
(Yamaoka et al. 2017). The presence of one or more metastatic lymph node(s) in colon cancer defines stage III disease.
Retroperitoneal, pelvic or inguinal lymph node enlargement
represent metastatic disease in patients with colon cancer.
CT has moderate accuracy for defining the N stage, which is
correctly predicted in only 62% of patients (Smith etal. 2007).
The sensitivity and specificity of CT for identifying metastatic
lymph nodes in colorectal cancer are 70% and 78% respectively
Assessing Lymph Nodes (N)
The lymph node distribution of the colon is classified into the
pericolic lymph nodes (D1), the intermediate lymph nodes (D2)
and the central lymph nodes (D3). The Japanese classification
(Dighe etal. 2010). Of note, pathologically enlarged nodes may
not contain metastatic cells and smaller nodes may have microscopic tumor involvement. Stage III disease is best predicted by
the presence of one or more lymph node(s) with a heterogeneous density and/or an irregular outer border (Figure 4).
194 2 COLORECTAL AND ANAL CANCER
https://t.me/medicina_free
Figure 4 Axial CT image (A) and coronal MPR (b) of a large T4a caecal tumor (asterisk) with an adjacent irregular, heterogeneous attenuation and
enlarged mesocolic lymph node (arrow). The combination of these imaging features is consistent with metastatic lymph node involvement.
Figure 5 Axial CT Colonoscopy study image (A) of a 3 cm polypoid mass within the ascending colon (arrow). Insufflation of the colon with carbon
dioxide distends the bowel wall, enabling identification of small polyps and the generation of virtual endoscopic, volume rendered images (B). The
corresponding optical endoscopic image (C) correlates well with that generated by CT. High density material within the bowel lumen in (A) represents
iodine-based oral contrast medium administered as part of bowel preparation – both to achieve a laxative effect and for “tagging” of any residual fecal
material, improving the detection of small polyps.
Excluding Synchronous Lesions
Synchronous colorectal cancer refers to more than one primary colorectal cancer diagnosed in the same patient at the
time of initial presentation. The prevalence of synchronous
colorectal cancer is close to 4% of patients (Latournerie etal.
2008; Mulder etal. 2011). This prevalence is of course higher
in patients with hereditary colorectal cancer, such as hereditary nonpolyposis colorectal cancer (HNPCC), familial adenomatous polyposis (FAP), MUTYH-associated polyposis
(MAP) and others, and in those with chronic inflammation
secondary to inflammatory bowel disease. Excluding
synchronous lesions in the lower gastrointestinal tract
Соседние файлы в папке Библиотека им академика М.И. Перельмана