Module 2.2: Intestinal Flashcards
(130 cards)
1
Q
Indications for oesophagus imaging
A
- Dysphagia
- Anaemia
- Pin
- Assessment of tracheo-oesophageal fistulae
- Assessment of site of perforation
2
Q
Contrast used in oesophageal imaging
A
o Suspension formed from Barium sulphate (stable in stomach acid)
o Good mucosal coating compared to water soluble agents e.g. gastrograffin good for looking at mucosal abnormalities
o Cheap
o Inert in lung no problem with aspiration (ionic agents draw a lot of fluid leading to pulmonary oedema)
o High morbidity if barium gets into peritoneal cavity (50% mortality) don’t give if there is a risk of perforation or if checking for anastomoses
• Water-soluble contrasting media
o These can be high or low osmolality contrast agents
High: gastrograffin
Low: omnipaque (safe but expensive)
o Ionic contrasts e.g. gastrograffin can cause pulmonary oedema if aspirated
o Best for assessing leaks/perforations as it is safe in the peritoneum
o Risk of allergic reaction (iodine content)
3
Q
Normal Anatomy of the oesophagus
A
• Oesophagus is generally divided into 3 parts:
o Upper, middle and lower thirds
• It pierces the diaphragm at T10
• Consists of A and Z rings
• Normal indentations seen on film of AP swallow include: pharynx, epiglottis and piriform fossa
• Normal indentations seen on lateral swallow include: epiglottis, venous plexus, cricopharyngeus muscle (protective mechanism in reflux: spasm and closes off when one swallows), aortic arch and left atrium
• Identification of aortic arch occurs at T4 and LA indentation, cricopharyngeus muscle
4
Q
Oesophageal pathology
A
- Dismotility
- Zenker’s Diverticulum/Pharyngeal Pouch
- Oesophageal Web
- Achalasia
- Oesophageal Varices
- Boerrhave Syndrome
- Oesophageal Cancer
- Oesophageal Ulcer
- Retro-oesophageal Thyroid
- Pseudodiverticula
5
Q
Dismotility in oesophagus
A
o Dimpling of the edges of the oesophagus
o These are tertiary contractions where the oesophagus is ineffectively propelling food down common in older ages as muscles do not work as normal
6
Q
Zenker’s Diverticulum/Pharyngeal Pouch
A
o Seen as outpouching at the level of pharynx
o Patient complains of regurgitation
7
Q
Oesophageal Web
A
o Benign stricture seen as a straight membranous band on AP and lateral views
8
Q
Achalasia
A
o Dilated oesophagus with food residue
o Beak-like tapering at the level of the gastro-oesophageal junction
o Lower oesophageal sphincter fails to relax
o Tertiary contractions
Absence of normal peristalsis and lack of relaxation of lower oesophageal sphincter critical to diagnosis
All due to failure of myenteric plexus
Gold standard investigation is manometry
Leads to recurrent aspiration pneumonia and oesophageal cancer
o Predominantly young patients
o Complications:
Recurrent aspiration and pneumonia
Risk of oesophageal cancer
9
Q
Oesophageal Varices
A
o Serpiginous filling defects (curly line with little oesophagus demonstrable)
o Porto-systemic venous collateral formation around oesophagus (seen through injection of contrast)
10
Q
• Boerrhave Syndrome
A
o Spontaneous perforation of the thoracic oesophagus
o Due to stretching
o 25% mortality
o See contrast extravasation into mediastinum
o Associated with pneumomediastinum/pleural effusion (L>R)
o Tends to be a complication of Mallory-Weiss tears
11
Q
• Oesophageal Cancer
A
o Irregular annular stricture of the mid-oesophagus (apple-core stricture and shouldering of contrast)
o Polypoid mucosal filling defects
o 95% squamous cell carcinoma, 5% adenocarcinoma
o Associations
Alcohol and smoking
Achalasia
Head and neck cancers
Adenocarcinoma commonest at the lower third due to Barrett’s
o Staging by EUS (wall extension and lymph nodes) and CT
12
Q
• Oesophageal Ulcer
A
o Ring-shaped lesion
o Fluid level seen due to barium filling
13
Q
• Retro-oesophageal Thyroid
A
o Benign lesion as one can see a smooth filling of barium on a narrowed oesophagus
o CT scan needed to confirm compression
• Pseudodiverticula
o Long stricture of oesophagus
o Several collections of barium seen
o Little ulcerations occur along the oesophagus
o Pathognomonic of infections such as candidiasis
14
Q
Contrast Agent in stomach imaging
A
• Barium E-Z HD 250%
o Higher density to provide good coating
• CO2 (carbex granules)
o Distends lumen of stomach allowing for double contrast effect
o Except in very ill or children
• Buscopan or glucagon
o Slow gastric emptying
o No effect on gastro-oesophageal junction
o Buscopan contraindicated in glaucoma/heart problem
• Water-soluble contrast agents used to assess site of perforation
15
Q
Indications for Barium Meal
A
- Dyspepsia
- Weight loss
- Upper Abdominal Masses
- GI Haemorrhage – Anaemia
- Obstruction
- Assessment of site perforation
Contraindications: complete large bowel obstruction
16
Q
Normal Anatomy of stomach
A
- Gastric fundus below diaphragm + body + antrum + greater/lesser curve of stomach + pylorus + start of duodenum
- Gastric rugae intact (lines across surface of stomach)
17
Q
Pathology of the stomach/duodenum
A
- Hiatus Hernia
- Benign Gastric Ulcer
- Gastric Cancer
- Linitis Plastica
- Fundal Diverticulum
- Gastric Polyp
- Bezoars (benign appearance wall is smooth)
- Gastric Varices
- Duodenal Carcinoma
- Duodenal Ulcer
- Ampullary Carcinoma
- Duodenal Diverticulosis
18
Q
• Hiatus Hernia
A
o Can be rolling or sliding
o Rolling: shows two round protrusions, one protruding from the other. Due to gastric fundus herniating through the gastro-oesophageal junction, hence the junction stays in the same place
o Sliding: involves gastro-oesophageal junction moving upwards towards the oesophagus, so that both the junction and fundus are found above the diaphragm. Extra constriction can be seen where the stomach starts.
o Predisposition to reflux
19
Q
• Benign Gastric Ulcer
A
o Contrast goes through into ulcer crater
o Typically oval or round, with surrounding radiating fold caused by scarring
o May project beyond the stomach wall (causing tethering of mucosa)
o Found on antrum or greater curvature of stomach
o Smooth collar of surrounding mucosa
o Ulcers look like nipples, with barium filling centre (or target sign if superficial)
20
Q
Gastric cancer
A
o Irregular polypoid mass, distortion of rugae, loss of normal gastric rugae
o 3rd most common GI malignancy
o Staging by EUS and CT
o 60% lesser curve, 30% on GOJ, 10% on greater curve
o May present as malignant ulcer, diffuse narrowing, ulcerated luminal mass, polypoid mass
21
Q
• Linitis Plastica
A
o Full circumferential narrowing of the stomach (small stomach)
o Most commonly caused by malignancy inflammation
o Commonest malignant causes are lymphoma and mets
o May also be caused by gastric carcinoma/local invasion
o Inflammatory causes (rare)
TB, Crohn’s, radiotherapy, corrosives
22
Q
• Fundal Diverticulum
A
o Benign lesion with a common appearance of an outpouching
23
Q
• Gastric Polyp
A
o Sometimes difficult to differentiate from ulcer
o Outer edges are blurred thereby implying a mass (reverse is seen in ulcer)
24
Q
• Bezoars
A
(benign appearance wall is smooth)
o Trichobezoars (hair) o Phytobezoars (plant matter) o Pharmacobezoars (chemicals) o Miscellaneous
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• Gastric Varices
o Can look like a malignancy
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• Duodenal Carcinoma
o Filling defect seen within lumen
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• Duodenal Ulcer
o Pooling of barium into a crater
o Common sight for ulcers is the duodenal cap
o Best visualised using gastroscopy
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• Ampullary Carcinoma
o Filling defect in the 2nd part of the duodenum
| o Form of cholangiocarcinoma
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• Duodenal Diverticulosis
o Outpouching fills with barium
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Indications of small bowel radiography
* Pain
* Diarrhoea
* Anaemia
* Partial obstruction
* Malabsorption
* Abdominal Mass
* Failed Small Bowel Enema
Contraindication: perforation + complete obstruction.
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Normal Structure of Jejunum and ileum
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• Jejunum
o Thicker walls
o Thicker valvulae conniventes (2mm) = feathery
o Left upper abdomen (by stomach)
o Thicker: 3-3.5cm
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• Ileum
o Thinner walls
o Thinner valvulae conniventes (1mm)
o Right lower abdomen
o Thinner: 2.5cm
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Crohn's
• Crohn’s = rose thorn ulceration (deep ulcers), discontinuous (skip lesions), cobblestone mucosa (oedema)
o Asymmetrical thickened folds with granular lumpy surfaces progress to inflammatory polyps
o Complications include: fistula, abscess, stricture (string sign of Kantor), perforation and cancer (e.g. small bowel lymphoma)
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• Meckel’s diverticulum
o Persistent remnant of the vitello-intestinal duct
o Rule of 2:
2% population affected
Within 2 feet of ileocaecal valve
Normally 2 inches in length
o Complications: GI bleeding, diverticulitis (inflammation), intussuception
o SBE shows blind pouch or anti-mesenteric border of ileum
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• Jejunal diverticulitis
o Outpouchings
| o Risk of malabsorption due to bacterial overgrowth
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coeliac
o Jejunum will show loss of its feathery appearance featureless jejunum
o Not usually seen as often is diagnosed before it can get to this stage
36
Anatomy of Colonic Crypt
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• Single stem cell dominates the crypt
• Crypts divide by crypt fission
o These will be clones of a single stem cell (the one that dominates crypt)
• Mutations spread this way
• Cancer is ‘clonal’
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• Zeki S, et al. Nat Rev. Gastroenterol. Hepatol. (2011): Pericryptal myofibroblats are found in the niche that produce growth factor signals, so that stem cells are directed to grow colon. There are various pathways that control this.
37
Wnt Signalling Pathway in the colonic crypt
• Controls upward migration from crypt niche
• Coordinates crypt growth by:
o Ligand binds to Wnt receptor FZD10
o Inactivates APC
o Stabilising beta-catenin
o This activates LEF/TCF transcriptional activators
* Ligand binds to Frizzled receptor preventing APC binding to beta-catenin
* Beta-catenin is able to then translocate to the nucleus and allow transcription and translation of Wnt target genes.
* In cancer, the Wnt signalling pathway is always activated thereby causing constant transcription and translation of target genes
* In normal cells, beta-catenin is then targeted for degradation by APC by a process of ubiquitalisation
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APC or beta-catenin gene mutations in CRC
o Occur both inherited and sporadic CRC
o Lead to constitutively activated Wnt pathway
o Loss of control of proliferation & differentiation
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TF-β Signalling Pathway in CRC
* Major inhibitory role growth i.e. cell cycle arrest?
* TGF-β signalling is integral to cell proliferation, differentiation, migration and apoptosis
* Pathway often deregulated in CRC
* Proteins include BMP, TGF, SMAD, GREM
Explanation of diagram:
• Genes of proteins highlighted in blue are implicated in GWAS
• Genes of proteins highlighted in purple are thought to be mutated in CRC (acquired)
• When activated TGF-beta binds to its receptors, this induces intracellular phosphorylation of SMAD2 and SMAD3
• These bind to SMAD4, and translocate to the nucleus to drive SMAD-responsive gene expression
• There is a SMAD independent pathway, which involves the activation of Rho-like GTPase such as RhoA
• RhoA then activate ROCK and RHN2 which regulate the gene expression of TGF-beta target proteins
40
Adenoma to Carcinoma Sequence
* Earliest form of pre-cancerous lesion: labyrinth crypt focus
* Black dots represent normal crypts
* This is a product of a single stem cell with enhanced growth factor
* Immune cells are able to detect this leading to apoptosis
* Adenoma
* May remain there for decades
* Cancer
* Thought that it takes ~17 years for a cancer to develop from normal mucosa
* This is thought to be associated with a number of genetic changes that cause increased proliferation and decreased differentiation
* APC is the common initiating mutation start process
* Subsequent mutations in oncogenes such as kRAS and BRAF lead to increased proliferation
* Hypo/hypermethylation is thought to occur across the genome leading to hypomethylation of proto-oncogenes or hypermethylation of tumour suppressor genes key event
* At the stage of hyper-dysplasia there is a loss or gain of chunks of chromosomes e.g. p53 loss
* In cancer, one sees increased cell density of crypts with a different morphology. They are now migrating through to the stroma due to disordered Wnt signalling. This process can be driven by inheritance of genes and exposure to carcinogens.
41
Inherited Risk Factors of Colorectal Cancer
• Lichtenstein et al 2000, NEJM: twin studies indicate that 35% of CRCs are due to heritable factors
• Everyone has a unique risk profile of protective and harmful risk factors (genetic and environmental) this can be modified by lifestyle to modified risk
• High/Low Penetrance
o Interaction between environmental and genetic factors
o Syndromes i.e. high penetrance vs more subtle risks i.e. low penetrance
o Care: diagram implies that if you have a high genetic risk you have a low environmental risk that is not necessarily the case, you can have both being high or even both being low
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• Looking at pathways implicated in high penetrance risk factors (syndromes)
o Wnt signalling
o TGF-beta
o DNA repair
o APC
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Single Nucleotide Polymorphisms
o Chromosome 6 hotspot one point strongly associated with the risk of CRC
• For the SNPs identified, the majority don’t confer a particularly high risk (e.g. allele that confers 21% increased risk will only increase your overall risk by 1%)
C-Myc
• Transcriptional activator that interacts with Wnt signalling
• Constitutively activated in cancer
• TGCA: aberrant expression in 100% of CRCs
• GWAS shows that risk alleles are shared among breast and prostate cancers also
TGF Pathways
• BMP2. BMP4, SMAD7, GREM1, RHPN2, CDH1
• Signalling pathway has potential for synergistic action
• Biological evidence
o TGCA
o Low risk: allele-specific expression of TGFBR1
o High risk: juvenile polyposis and HMPS
GREM1
• Previously known as CRAC1 locus
• BMP signalling antagonist
• Upstream mutation results in increased GREM1 (resulting in HMPS in Ashkenazi Jews)
• Lower penetrance variants associated with CRC risk in general population
• Analogous with high penetrance APC mutation in FAP and lower penetrance APC T3920A
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Acute Upper GI bleeding (AUGIB) presentations
• Haematemesis
o MUST be proximal to ligament of treitz (DD, oesophagus, stomach) i.e. it is an upper GI bleed
o Bright red vs coffee ground
• Melaena
o Anywhere from mouth to caecum, but most common due to upper GI bleed
o Coffee ground haematemesis or malaena indicate digested blood
• Bright red rectal bleeding
o Most common anorectal/colonic
o Can occur from upper source- e.g. if have massive GI bleed (e.g. from stomach) fast Transit time bright red rectal bleeding + shock
• Maroon or dark red stools
o Difficult to distinguish location
o Can come from SB or more proximal or colonic sources or UGI tract
o More commonly lower GI tract
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Causes of AUGIB
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o Peptic ulceration
o Oesophagitis
o Gastritis
o Duodenitis
o Varices less common – but still important
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Peptic Ulceration
• Most common causes of ulcers
o NSAIDs/aspirin
o H. Pylori
o Idiopathic
Bleeding is exacerbated by anticoagulation: Warfarin, Clopidrogel, NOAC
Classification
1. Major stigmata – non bleeding visible vessel
o Ulcer is white/yellow exudate, red spot is visible vessel (see right)
o Ulcerate extends down and exposes vessel bleeds, and then stops.
2. Adherent clot, overlying ulcer
o Clot removal usually attempted – with snare (right)
o Underlying lesion can then be assessed, treated if necessary
o Role of endoscopic therapy of ulcers with adherent clot is controversial
3. Minor stigmata
o Most ulcers do not have visible vessels
o Low re-bleeding risk – no endoscopic therapy needed
o A) Flat pigmented spot (below, left) B) clean base (below, right)
• Forrest classification is used for PUD bleeding, to aid risk stratification
o Arterial jet – most high risk (30-40% without treatment, treatment reduce <15%)
o Low risk do not require endoscopic treatment
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Treatment of Non-Variceal UGIB
• If Hb low Blood transfusion
• If stigmata of haemorrhage Endoscopic therapy
o STANDARD endoscopic therapy: combination therapy: adrenaline + thermal therapy/clips
Injection of adrenaline around vessel tamponade vessel cause it to clot.
High rates rebleeding (20-30%) unless combined with other therapy (reduce to <10%)
Thermal therapy – burn vessel risk perforation
Clips
• Angiographic embolization
o Radiologists inject die in arteries. Localize extravasation of contrast
o Insert material e.g. coil
o Useful for when endoscopic therapy fails or elderly who are not candidates for surgery
• Surgery – when other therapies failed
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Varices
• Much higher rate of mortality and bleeding can be more severe mostly due to cirrhosis
• Cirrhosis portal HTN collaterals varices
• E.g. oesophageal (above), gastric (below), rectal
• Risk of bleeding depends on size and stage of cirrhosis
• Blood transfusion (restrictive)
• Antibiotics
o Higher risk of infection in cirrhosis (bacterial translocation) made worse in decompensation, caused by variceal breading. ABx reduce risk death.
o NB bacterial translocation: the passage of viable bacteria from the gastrointestinal (GI) tract to extraintestinal sites, such as the mesenteric lymph node complex (MLN), liver, spleen, kidney, and bloodstream. Mechanisms proposed: (a) disruption of the ecologic GI equilibrium to allow intestinal bacterial overgrowth, (b) increased permeability of the intestinal mucosal barrier, and (c) deficiencies in host immune defences. Intestinal barrier damaged blood. Or intracellular route through epithelial cells LN onwards.
• Terlipressin
o Portal HTN causes splanchnic vasodilation and increased portal pressure
o Terlipressin is a splanchnic vasoconstrictor reduces pressure in splanchnic bed and therefore in varices
• Endoscopic therapy
o E.g. rubber band ligation (right)
• TIPPs – transjugular intrahepatic portosystemic shunt
o Shunt between portal and hepatic vein - to decrease pressure in portal vein
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Outcome of AUGIB
• Most (> 80%) stop spontaneously and do not require any treatment
o Low –risk endoscopic lesions or normal endoscopy
• 20% require therapy
• Rebleeding
o Highest for treated bleeding vessels and varices: 10-20%
• Mortality can be has high as 10-20 % especially if elderly, comorbid disease, variceal bleeding
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Risk stratification of AUGIB
* Needed to assess the risk of: requiring an intervention, rebleeding or death.
* Currently vast majority of patients admitted to hospital for observation and endoscopy, regardless of severity. In the majority this is unnecessary (low risk).
* Better to identify low and high risk groups at admission to allow for treatment/early discharge
* British guidelines (SIGN) previously recommended the pre-endoscopy (admission) Rockall score, now GBS
Models
• Multiple logistic regression based models
o Rockall
o Glasgow Blatchford score
o Set of data, look for no of variables that may affect outcome – identify predictive variables
• Machine Learning based models
o Artificial neural networks
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Rockall
* Rockall et all Gut 1996: Prospective evaluation of two cohorts AUGIB (4185 and 1625 cases)
* Aim to analyse risk factors for death and develop a clinically useful risk score
* Multiple logistic regression based
• Multiple publications in different countries showing accurate in predicting death (>80%) and rebleeding (75%)
o Vreeberg et al Gut 1999
o Phang et aL N Z Med J 2000
o Sanders et al Am J Gastro 2002
* Most widely used post-endoscopic risk score widely validated in various populations
* However may not affect clinical decision predicts rebleed but doesn’t predict need for intervention.
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Glasgow Blatchford Score
• Blatchford et al, Lancet, 2000: Glasgow Blatchford Score (right)
• Developed based on 1748 patients with AUGIB
• Used MLR to develop a risk score to predict need for blood transfusion, clinical intervention, rebleeding and death (inpatient stay)
• Validation in 197 patients
• Found that score discriminated those who required treatment (AUROC: 0.92)
o Compared this to Rockall score
51
Rockall vs GBS
* Rockall not as good at predicting treatment
* Glasgow more useful clinically at discriminating those who required treatment higher true positives
• Chan JCH, Ayaru L. Analysis of risk of scoring for the outpatient management of AUGIB – Frontline Gastro 2010
GBS significantly more accurate (0.82; 95% CI (0.78 to 0.86) than pre-endoscopy Rockall (0.71; 95% CI 0.67 to 0.76) – both sensitivity and specificity
NICE recommends GBS to determine whether to discharge patients.
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What are Artificial Neural Networks
• Non-linear statistical models
• Look for relationships between input variables and given outcomes
• Learning – train model on dataset to get increasing accuracy.
• Often identify complex relationships missed by linear models
• GBS and Rockall limited
o Not very specific
o Risk assessment conventionally involves inpatient OGD
o Accurate and reliable non-endoscopic risk score would help identify low risk save resources and protect patients from inpatient harm
• Das et al Gastroenterology 2008: Developed an ANN based model for the non-endoscopic triage of patients with non-variceal AUGIB
o Small numbers: 387 patients
o Looked at non-variceal bleeds (internal an dexternal cohorts)
o Outcomes: predict major stigmata of recent haemorrhage and need for endoscopic therapy (27 variables inputted)
o Sensitivity >80% , Negative predictive values >92%
• Ali A et al, Artificial neural network as a predictive tool for the risk stratification of acute UGI bleeding, 2012
High specificity, accuracy in predicting large number of outcomes.
Limitations: retrospective, low sensitivity (significant no. high risk misclassified as low risk) compared to Blatchford
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Acute Lower GI bleeding
* Compared with AUGIB , ALGIB are significantly less likely
* Stops spontaneously in the majority (80–85%) of patients
* Overall mortality rate ranges from 2% to 4%
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Aetiology of ALGIB
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Aetiology
• Diverticulum
• Angiodysplasia
• Colitis (ischaemic, infections, IBD, radiation)
• Neoplasia, post polypectomy bleeding
• Anorectal disease (including varices)
• UGIB
• SB bleeding
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55
Tx of ALGIB
• Blood transfusion
• Endoscopic therapy – less well established compared with AUGIB
o Clipping of vessels
o Banding of haemorrhoids
o Argon plasma coagulation of angiodysplasia
o +/- adrenaline
• Interventional radiology – embolisation of vessels (1st choice for haemodynamically unstable bleeds, as colonoscopy difficult to visualize bleeds)
• Surgery – rarely used as difficult to localize
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ALGIB Risk Scores
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Multiple Logistic Regression based Risk Score
• BLEED 1998
found to be a poor source by Das et al 2003
o Quantitative variables
SBP <100
>19.2s PT
o Qualitative subjective
Unstable comorbidity
Ongoing bleed in A&E
Erratic mental status
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• STRATE et al 2005
o 0 = low risk, 1-3 = moderate, >3 = high risk
o Quantitative variables:
Systolic BP <= 115 mmHg
HR >=100/min
o Qualitative, subjective variables:
History of syncope
>2 comorbidities
Aspirin use
Non-tender abdominal exam
Rectal bleeding within 1st 4hrs of evaluation
• Accuracy of score about 75% (not as good as UGI scores)
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Oakland et al, Derivation and Validation of a Novel Risk Score for Safe Discharge after ALGIB: A Modelling Study, Lancet, 2017 (see right)
o Age, sex, previous admission for lower gastrointestinal bleeding, rectal examination findings, heart rate, systolic blood pressure, and haemoglobin concentration strongly discriminated safe discharge in the development cohort (C statistic 0·84, 95% CI 0·82–0·86) and in the validation cohort (0·79, 0·73–0·84).
The score was better than Rockall, Blatchford, Strate, BLEED, AIMS65, and NOBLADS scores in predicting safe discharge. A score of 8 or less predicts a 95% probability of safe discharge.
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Artificial Neural Network for ALGIB
• Das et al, Prediction of outcome in acute LGI haemorrhage based on ANN: internal and external validation of a predictive model, Lancet, 2003:
o Prospective study (small numbers, internal: 120, external: 70) comparing ANN and BLEED and MLR
o Outcomes: Recurrent bleeding, therapeutic intervention and death
o Many input variables
o Very accurate results: Death and recurrent bleeding 80-90% accurate
o Limitation: not been revalidated
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Background to Endosonography
• High frequency miniature ultrasound transducer is incorporated into the tip of a conventional endoscope resulting in enhanced resolution of the GI wall and structures with close proximity to the GI wall
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Advantages to USS
* High intrinsic spatial resolution
* No ionizing radiation
* Inexpensive and easily portable
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Disadvantages to USS
* Gas and bone impede the passage of USS waves
| * As good as the operator
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Types of Echoendoscopes
• Radial
• Linear
• Miniprobes
o Thin fibre-like probes no longer used in clinical practice as linear and radial are much better
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Indications to EUS
• Staging malignant GI tumours of oesophagus, stomach, duodenum, rectum, ampulla of Vater, extrahepatic bile ducts and pancreas.
• Obtain FNA/Biopsy of lesions in accessible organs including mediastinal lymphnodes
• Best imaging modality to characterise GI sub-mucosal lesions
• Investigate presence/causes of acute and chronic pancreatitis
• Investigate choledocholithiasis
• Investigate unexplained mediastinal and upper abdominal lymphadenopathy
• Therapeutic
o Perform coeliac plexus block
Used for pancreatic cancer reduce pain
o Perform a Cyst-Gastrostomy
Create an opening between a pancreatic pseudocyst (pancreatitis complication) and the stomach
o Facilitate biliary and pancreatic access when ERCP fails
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Complications of EUS
• Diagnostic EUS-related
o Perforation
o Bleeding
o Sedation related cardiorespiratory problems
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• Therapeutic EUS-related
o Bleeding (1%)
o Perforation (<1%)
o Acute pancreatitis (0.9%)
o Infection (0.1%)
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EUS in Oesophageal Cancer
• Staging using EUS layers can be seen on EUS and so tumour stage can be determined
o T1 mass: tumour has invaded lamina propria (and submucosa)
o T2 mass: tumour ha invaded muscularis propria
o T3 mass: tumour has invaded adventitia
o T4 mass: tumour has invaded adjacent structures
• Staging Significance of TNM
o If tumour not infiltrating the muscularis mucosa (Tis) then 0 % local lymphnode infiltration
o If tumour infiltrating the muscularis mucosa (T1m) then 0-10 % local lymphnode infiltration
o If tumour infiltrating the submucosa (T1sm) then 0-43 % local lymphnode infiltration
o The deeper it goes, the greater the risk of lymph node metastasis due to closeness of lymph nodes to muscularis propria
o The stage determines whether resection is advised
• EUS can be used for mucosal resection of T1 tumours (up to T1sm)
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EUS in Gastric Cancer
• Not used often patients often present with more advanced disease, EUS is more useful in early disease
• Useful for submucosal tumours/extrinsic compression
• Useful in local-regional staging of Gastric Ca in early disease
• Useful in assessing the extent in the oesophagus
o Useful for surgeons to assess how much resection is needed
Gastrointestinal Submucosal Tumours
• Any growth underneath the mucosa of the GI tract
• Normal overlying mucosa on biopsy
• GI Stromal tumours (GISTs) the most common (1 % of GI tumours)
o Guidelines: any GIST >2cm has to be removed
• Mesenchymal cell origin
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EUS in Duodenal Cancer
* Assessing the extent of ampullary adenomas/malignancies
| * Can even be used to remove ampullary tumorus (ampullectomy) if they are very early with no sign of metastases
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EUS in Pancreatic Cancer
• Post-operative 5 year survival for pancreatic Ca is 20 %
• Incomplete resection and positive nodes carry bad prognosis
• EUS may help to better select patients for curative surgery or to identify the non-surgical candidates
• EUS can be used in:
o Detection
o Staging
o Assess vascular invasion
o Resectability
• Comparison of EUS and other imaging modalities in Mx of pancreatic cancer
o EUS often has better definition of lesions <2-3cm
• Progress has been made with elastography and analyse the strain ratio (compare rigidity of normal and cancerous tissue)
• EUS can also be used along with ERCP to locate gall stones which may have migrated into the common bile duct
• EUS can be used to drain pseudocysts (EUS cyst-gastrostomy) EUS has the greatest long term success, and least morbidity and mortality compared to other modalities
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EUS in Coeliac Nerve Block
* It is an injection of local anaesthetic into the coeliac plexus
* Done as part of the treatment of chronic pancreatitis and other types of chronic abdominal pain
* Relatively easy and safe to perform
* Similar success rate to other methods but less invasive (~70-80%)
* Diarrhoea main complication
* Useful in pancreatic cancer related pain but not in CP
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Screening vs surveillance
* Screening: average risk population
| * Surveillance: high risk groups e.g. previous neoplasia, IBD, FH, etc
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Criteria for Screening
(Wilson & Jungner 1968)
* Important health problem
* Accepted treatment
* Facilities for diagnosis and treatment
* Latent or early symptomatic stage
* Suitable/Acceptable screening test
* Natural history understood
* Financially viable
Colorectal cancer fulfils all of criteria.
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Aim of Screening
• Reduce mortality by decreasing incidence and earlier detection
• It is important to take into account lead time bias
o Limited benefit for B: detect earlier than would present, but do not prolong survival i.e. worried for longer
o Benefit for C: live longer
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Types of Screening
Organised vs Opportunistic
Non-Endoscopic vs Endoscopic
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Organised (Population)
• Invitation
• Maximise benefit to population
• Minimise harm to population
• High specificity (low false +ve)
• May not be most sensitive
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Not necessarily the gold-standard, it is allowed miss some people who have the disease.
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Opportunistic (Individual)
(Only done in America)
• Individual
• High sensitivity
• Harm less important
• Tailored to individual
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Non-Endoscopic
• Often more suited to screening
• Often rated high by subjects – NO discomfort, bowel prep, embarrassment, lost time in work
e.g. FOBt, FIT, Molecular stool testing, Virtual colonoscopy
Endoscopic
• More sensitive (low false –ve)
Unlikely to do harm if you are fit and well but if used as a screening programme, for many reasons. Most importantly you are likely to do harm given the fact that the people you see you will not know them (or their medical conditions, medications etc), this is irrespective of cost, feasibility etc.
• More appropriate for opportunistic screening
e.g. Colonoscopy, Flexi-Sigmoidoscopy
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FOBt (faecal occult blood test)
* Detects blood in stool
* Relies on pseudoperoxidase activity of haem
* Facilitates oxidation of guaiac when hydrogen peroxide added
* Need to do 6 samples
* USED IN BCSP IN UK
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benefits of FOBt
Safe
Evidence of efficacy
Detects cancers early
Acceptable uptake (compliance 45-65% for first test)
Acceptable colonoscopy rate – cumulative colonoscopy rate ~4%
- Mandel, Lancet, 1993: decrease mortality 33% (annual screening – ignore as it is not similar to what is currently done)
- Hardcastle, Lancet, 1996: decreased mortality 15% (England)
- Kronborg, NEJM, 1996: decreased mortality 18% (Denmark)
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Limitations of FOBt
Low sensitivity (misses people who have disease)
| False positives: Interference from food/drugs/other conditions e.g. aspirin, haemorrhoids etc
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FIT
| faecal immunoassay test
* Immunoassays for human haemoglobin i.e. monoclonal Ab against human Hb
* One of two faecal samples
No dietary restriction
May be quantitative or qualitative - ? set thresholds of risk – the lower you set the level the more colonoscopies you will have to do
Only required to swab surface of stool
77
Molecular testing in CRC screening
* In normal colon: epithelial cells die, apoptose and are continuously exfoliated into stool
* Inadenoma/adenocarcinoma: intact cells are shed into stool
78
Molecular testing advantages and limitations
Increased sensitivity and specificity
Ability to test for mutations in intact cells
Scooped stool = patients prefer it as they don’t have to scrape anything reduced contact with stool
Bacterial DNAases degrade DNA add EDTA buffers
Inhibitors to PCR present in stool collection buffer dilutes, homogenisation, addition polyvinylpolypyrrolidone
Scooped sample may decrease compliance, however patient contact with stool reduced
Expensive (shipping whole stool)
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Virtual Colonoscopy
| /CTC
* Uses CT imaging – have a colonoscopy without physically having one
* No longer used in practice
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Advantages and limitations of virtual colonoscopy
Increased patient satisfaction (no bowel prep)
Safe
No sedation
Extra-colonic information can also be a problem as can pick up abnormalities in pancreas (for example) that may not be significant)
Sensitivity & specificity comparable to colonoscopy? depends on operator, hence it may not be as good as colonoscopy in the grand scheme of things
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Most available data obsolete
Availability of resources
High quality equipment
Requires skilled interpretation
? Small polyps may not be of significance and you will have to do a colonoscopy anyways
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Colonoscopy
* Gold-standard for examination of colon
* Included in AGA guidelines as option for screening (screening modality used in US only)
* Reserved for therapy/surveillance in UK
82
Advantages and limitations of colonoscopy
High sensitivity and specificity
Ability to biopsy
Therapeutic opportunity
Risk
Discomfort/embarrassment
Bowel prep
Sedation required
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Flexi sig
* Examines L colon
* Detects adenomas
75% neoplasia within reach of F/Scope
No sedation/Enema only
Quick
Identifies high risk individuals
Therapeutic / may prevent CRC
Significant reduction in CRC may be achieved by a single examination
Can be performed by non-medical personnel
Discomfort/embarrassment
Unable to test for lesions in R colon
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BCSP – Bowel Cancer Screening Programme
• FOBt testing for age 60-74 by invitation, biennially, available to >74 years on request
o Reasons for choice including:
Evidence of efficacy: 3 RCTs (see table)
Acceptable uptake
Acceptable colonoscopy uptake
Decreased mortality
o Results
Detects earlier cancers
Compliance is good – 45-65% for first tes
Cumulative colonscopy rate is feasible – 4%
• If abnormal result sent to screening centre colonoscopy
• Rolled out in 2010: 5 Hubs distribute tests, ~60 screening centres
o Invitation/kit sent
o Reminder sent if not return in 4 weeks
* Normal result (6 negative samples) FOBt offered in 2 years if <70
* Abnormal result (5 or 6 positive samples) offered colonoscopy
* Unclear result (1-4 positive samples) either 1 or 2 repeat kits dispatched
* Spoilt kit/technical fail 1 repeat kit dispatched
• Unsuitable for colonoscopy virtual colonoscopy (determined by doctor)
• Colonoscopy findings:
o Nothing abnormal FOBT offered in 2 years if < 70
o Cancer refer
o Other pathology refer/treat/advise
o Polyp
Low risk: 1 or 2 small (<1cm adenomas) FOBt in 2 years if <70
Intermediate risk: 3 or 4 small adenomas OR at least 1 adenoma >1 cm 3 yearly colonoscopy surveillance until 2 negative exams
High risk: >=5 adenomas or >= 3 adenomas of which at least 1 is >= 1cm colonoscopy after 12m, followed by 3 yearly colonoscopy surveillance until 2 negative examinations
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The ICRF/MRC flexible Sigmoidoscopy Trial
Once only’
• Age 55-64 years
• All polyps <1cm removed at screening
• Colonoscopy for those with high risk polyps
Initial Results – Lancet 2002
• 40,674 examinations
• High compliance (72%)
• High satisfaction (98% Glad) acceptable despite it being embarrassing etc.
• High pick up rates (12.1% Adenoma, 0.3% Ca)
• Safe (1 perforation, 1 bleed)
• In individuals screened: incidence CRC decreased by 33%, mortality from CRC decreased by 43%
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Flexi-Sig vs FOBt
* F-sig adenoma detection rate high (121 vs 5.8 per 1000 people screened)
* With F-sig: all get invasive procedure
* With FOBt: only few with positive result get invasive procedure (colonoscopy – which has high sensitivity)
* F-sig does not study the proximal colon so FOBt still has role
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CRC surveillance in Acromegaly
• Regular screening starting from 40 yrs
• Frequency dependent on findings at original colonoscopy
o Adenoma or increased IGF-1 levels repeat every 3 years
o Otherwise every 5 years
• Needs total colonoscopy (although may be difficult!)
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CRC Surveillance in Inflammatory Bowel Disease
• Up to x15 increased risk
• UC = Crohn’s
• Dependent on:
o Extent of disease and
o Length of diagnosis
o Disease Activity
• Sclerosing cholangitis added risk factor tends to go with UC and so colonoscopies done every year for these patients
• Colonscopy surveillance depends on whether patient is low, medium or high risk
o Low risk: offer colonoscopy at 5 years.
o Intermediate risk: offer colonoscopy at 3 years.
o High risk: offer colonoscopy at 1 year.
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GI Endocrine Tumour types
o Non-functioning
o Functioning – secrete a wide range of hormones
7% produce more than 1 hormone
90
Non-Functioning Tumours
• Can reach a large size in an apparently well patient
• Often mistakenly identified as adenocarcinoma
• Produce non-functionally active peptides e.g. pancreatic polypeptide and neurotensin
o i.e. peptides produced are not biologically active
• Stain with neurone specific enolase chromagranin
91
Functioning Tumours
• Usually present with symptoms of hormone excess
o Insulin
o Gastrin
o Glucagon
o Serotonin
o Somatostatin
o Vasoactive Intestinal Polypeptide (VIP)
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Diagnosis of functional GIT
• Fasting plasma sample raised hormone levels
o Why fasting? gut hormones increase when you eat
• Other causes of raised hormone levels must be excluded
o All hormones raised non-fasting or chronic renal failure
o Insulin sulphonylurea treatment
o Gastrin hypercalcaemia, achlorhydria (deficiency of HCl hence a physiological secondary gastrinaemia), PPI/H2 antagonist (these block HCl production and hence are an iatrogenic physiological secondary gastrinaemia)
o Glucagon hepatic failure, OCP, prolonged fast/stress
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Gastrinoma
• Syndrome results from excess gastrin stimulated acid production
Clinical Features
• Classic Triad
o Fulminating gastric ulcers (multiple and at atypical sites)
o Recurrent ulceration despite therapy (i.e. ulcers are resistant to therapy)
o Non -Beta cell pancreatic islet cell tumour
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• Other clinical features
o Diarrhea (severe in 40%) diarrhea without ulceration in 7%
o Steatorrhea (enzyme inactivation pancreatic lipase and mucosal damage)
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Background
• Incidence: 1 in 1 million per year
o Uncommon hence you must have an index of suspicion
• Majority are pancreatic
• 20-40% are duodenal micrograstrinomas (MEN-1: parathyroid, pancreatic, pituitary)
o These patients tend to have multiple small tumours and so resection will not cure disease
• 50% have metastases at diagnosis
• 60% are malignant
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Diagnosis of Gastrinoma
* Gastrin >40pmol/l
* Must be a fasted sample
* Patients must be off anti-secretory medication (PPI for 2 weeks and H2 antagonists for at least 3 days)
* Measure gastric acid secretion if there is doubt on diagnosis
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Tx of gastrinoma
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• Reduction in tumour load
o Surgery
o Hepatic embolisation
• Proton Pump Inhibitors
o Labile in acid therefore should be given initially with H2 blocker
• Octreotide
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• Localisation vs Blind Resection
o Aim of localisation – detect primary tumour and exclude metastases
• Advantages of localisation pre-operatively
o Allows planning of minimally invasive surgery (laparascopic/enucleation)
o Increases chances of cure
o Reduces need for repeated operations
o Reduces post-op complications
• Curative surgical resection more likely if preoperative localisation achieved
• >90% of gastrinomas are found in the GASTRINOMA TRIANGLE (see right)
o Third part of the duodenum
o Neck of the pancreas
o The porta hepatis
• 20% DUODENUM
• Localisation achieved via
o CT
o MRI
o Endoscopic US (EUS) 80-90% sensitivity
o Octreotide scan – radiolabelled octreotide analogue injected IV and taken up by tumours expressing somatostatin receptors (2 & 5)
o Angiography and Selective Arterial Stimulation and hepatic Venous Sampling (ASVS)
Localises tumours too small to be detected by other imaging (up to 50% of these tumours)
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Insulinomas
* Incidence 2 in 1 million per year
* 90% Benign i.e. 10% malignant
* 10% multiple
* 10% MEN1
* Median age 6th decade
* Tumours are usually small 0.5 to 5cm and occur in any part of the pancreas
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Clinical Features – Insulinoma Syndrome
• Neuroglycopenic symptoms
o Funny turns especially after fasting
o Altered mood, behaviour and personality
o Neurological disturbance
• Autonomic symptoms
o Palpitations
o Tremor
o Sweating
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Diagnosis of insulinoma
• Prolonged supervised fast
o Used to demonstrate fasting hypoglycaemia and diagnose insulinomas
• Preparation
o Admit to perform test under close supervision with glucose (PO/IV) available
• Method
o Cannulate patient and commence 72 hr fast.
o Water/non-caloric beverages allowed. Patient should be active during waking hours.
o Blood glucoses should be done at regular (4–6 hr) intervals and whenever the patient has symptoms suggestive of hypoglycaemia.
• If blood glucoses are ≤ 2.2 mmol/l or symptoms are convincing:
o Take blood for glucose, insulin and C-peptide
o Take blood and spot urine for sulphonylurea screen
o Ring biochemistry up for an urgent glucose.
o Do not reverse hypoglycaemia until the lab confirms hypoglycaemia, or unless the patient becomes unconscious or fits.
• If no symptoms during the fast, finish with 15-30 mins exercise, e.g. a brisk walk around the hospital. Take final samples for glucose, insulin and C-peptide, sulphonylurea screen.
Insulin (mU/L) C-peptide (pmol/l) Diagnosis
>6 >300 Insuloma
– ketones must be negative
<3-6 100-300 ?insulinoma
<3 <75 Normal
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Treatment of insulinoma
• Localisation achieved via
o CT
o MRI
o Endoscopic US (EUS) 80-90% sensitivity
o Octreotide scan – radiolabelled octreotide analogue injected IV and taken up by tumours expressing somatostatin receptors (2 & 5)
o Angiography and Selective Arterial Stimulation and hepatic Venous Sampling (ASVS)
Treatment
• Medical treatment is poor
o Multiple, regular, small meals à leads to weight gain (obesity)
o Guar gum - slows gastric absorption.
o Steroids – helpful for a short period. à can cause Cushing’s long term
o Diazoxide – s/e hyperkalaemia and severe oedema
o Octreotide – s/e hypoglycaemia if glucagon levels are suppressed.
• Surgery
• Hepatic embolization
o Liver has a dual blood supply (hepatic artery and portal vein)
o Embolization of hepatic arterial supply (which supplies tumour) using foreign substances e.g. polyvinyl alcohol
o Patent portal circulation is necessary to sustain liver function
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Should MEN-1 Patients who have Gastrinomas have routine surgery?
• Much debate between surgeons and endocrinologists on whether these patients should be operated
• Much of the evidence presented suggests that removing tumours/pancreas (if tumour not localised) can increase survival rates (retrospective and, prospective but not randomised studies)
o BUT – evidence is biased either not randomised, retrospective, or selective of patients
• It is essential that all doctors and especially those who read papers for evidence also read the discussion
• Surgery may not really be good
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Glucagonoma
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Background
• Incidence: 1 in 20 million
• Alpha cell tumour of pancreas
• Invariably pancreatic primary
• 75% have metastasized at diagnosis
• Rarely found in association with MEN1
• Diagnosis is not usually a problem as these tumours are massive
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Clinical Features
• Impaired glucose tolerance Diabetes Mellitus
• Venous thrombosis
• Normochromic normocytic anaemia
• Decreased weight
• Necrolytic erythema migrans
Diagnosis
• Increased Glucagon 10 to 20 fold
• Localisation almost never a problem
• Barium studies often show: thickened jejunal and ileal mucosa due to trophic effect of large forms of glucagon on the small bowel.
• 50% produce pancreatic polypeptide
• Coproduction of gastrin and insulin have been described
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Treatment
• Surgery
• Hepatic embolization
• Octreotide
• Zinc supplements
o Used to treat necrolytic erythema migrans (due to zinc deficiency theory: glucagonoma is using zinc to produce glucagon)
• Insulin
• Warfarin
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Somatostatinoma
• Rare: 1 in 40 million
• Increased concentrations of somatostatin in fasting blood sample
• 50% present in the pancreas, 50% duodenal
• Half of duodenal ones are associated with Von Recklinghausen’s disease (neurofibromatosis type 1): cafe au lait spots, neurofibromas and phaeocytoma risk
• TRIAD of symptoms
o Somatostatin suppresses exocrine pancreatic function, so steatorrhoea and malabsorption result (can be helped with Creon)
o Gallstones as gallbladder sluggish
o Impaired glucose tolerance and diabetes
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VIPomas
• Vasoactive Intestinal polypeptide
• Incidence: 1 in 10 million people
• 90% in pancreas, 10% from sympathetic chain
• 50% are malignant
• Symptoms
o Watery diarrhoea
o Hypokaleamia
o Achlorhydria (secretory diarrhoea without steatorrhea)
o Flushing
• Severe dehydration and loss of potassium and bicarbonate
• Unusual case of: hypokalaemic ACIDOSIS
• VIP also suppresses gastric acid production
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Carcinoid Tumours
* Can occur anywhere in the primitive gut: Foregut, midgut, hindgut
* Can be bronchial carcinoid, for example
* Only 3-5% of patients with carcinoid tumours will go on to develop the carcinoid syndrome
* Tumours make serotonin
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Carcinoid Syndrome
• Symptoms of:
o Diarrhoea, weight loss
o Sweating, facial flushing
o Bronchoconstriction
• Probably due to 5-hydroxytryptamine and tachykinins
• Only 3-5% of patients with carcinoid tumours will go on to develop the carcinoid syndrome – why?
o Of patients with carcinoid syndrome, 70-90% of those with carcinoid tumours have midgut carcinoids
o Hormones from midgut likely to be metabolised on first pass through liver, preventing symptoms.
o Hence, carcinoid syndrome only presents when tumour has metastasized to liver
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Causes of Carcinoid Syndrome
* Debated: 5-hydroxytryptamine = serotonin, 5-hydroxytryptophan (5HTP), tachykinins?
* 5-hydroxytryptophan (5HTP) injections do not cause flushing
* 5HTP antagonists do not reverse flushing but do improve diarrhoea
* Tachykinins?
* There are probably a large number of substances that are secreted by these tumours, hitherto unidentified
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Pre-Operative Localisation of carcinoid tumour
• CT, US and Levovist (microbubble contrast for US) scanning
• EUS
• Angiography
• Octreotide scanning
o Indium labelled DTPA-octreotide
o Spleen has many octreotide receptors: hides tail of pancreas
o Sensible to do this first
o Then perform CT scan with fine cuts through the area found on octreotide scan see slides to see this
o Gallium 68 labelled DOTATATE
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Prognosis of carcinoid syndrome
• Indeterminate
• If presenting with “syndrome”, liver or other metastases likely to be present
• If primary in small intestine, 5y survival 33-77%
• If primary in appendix, 5y survival 76-100%
o Only 2-5% of appendiceal carcinoids will metastasize
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Management of carcinoid
• Remove primary from bowel to prevent future obstruction
• Symptomatic treatment with somatostatin analogues
o Octreotide administered every 8h
o Lanreotide LA administered every 14 days
o Octreotide LAR adminstered every 28 days
o Lanreotide autogel
• Somatostatin analogues provide reasonable symptomatic control
o Tend to need to increase frequency of injections after 1-2 years
o Octreotide LAR vs; lanreotide LA
o Different tumours respond differently to each (symptoms)
• Hepatic embolization (see above for details)
o Mets only derive supply from hepatic artery
o Thus occlusion of hepatic artery results in selective loss of tumour
• Chemotherapy
o Streptozotocin + 5 FU
o streptozotocin + cyclophosphamide
o No evidence of any benefit
• Interferon alpha
o Studies suggest 12-48% response rate when used in combination with surgery
o Recent evidence disappointing
• Everolimus (mTOR inhibitor) and Sunitinib (tyrosine kinase inhibitor)
o Recent papers identify these as survival benefits
o Beware that evidence was financed by drug companies
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Principles of Radioimmunoassay
Confirming Diagnosis of Gut Hormone Tumours and Localisation of Tumours
• Unlabelled antigen (standard or sample)
• Mixed with fixed amount of corresponding radiolabelled antigen and a highly specific antibody
• Unlabelled (patient’s antigen levels) and labelled antigen (fixed amount) compete for the binding sites on the antibody
• Amount of bound labelled antigen is inversely proportional to the amount of unlabelled antigen.
• Once equilibrium attained, the antibody-bound and free antigen are separated and the radioactivity in the bound fraction is measured.
• Efficient separation of the bound and free radioactivity is essential.
o I.e. if patient has very little hormone in plasma, less of it binds to antibody and so more of the radiolabelled antigen will be measured (hence inversely proportional)
o The opposite is seen in those with gut hormone tumours more hormone is present hence more binds to the antibody and less radiolabelled fractions are measured
110
Expression Profiling using cDNA Microarrays
– Duggan et al, Nature Genetics, 1999
• Used to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome
• Collection of microscopic DNA spots are attached to solid surface
o Each spot contains specific DNA sequence (probes)
o These are used to hybridise a cDNA sample (target) under high-stringency conditions
• Complementary nucleic acids are paired up
• Non-specific bonding sequences are washed off, and only strongly paired strands remain hybridised
• Fluorescently labelled target sequences that bind to a probe sequence generate a signal
• Microarrays use relative quantitation in which the intensity of a feature is compared to the intensity of the same feature under a different condition
111
What regulation of Gene Expression in the Intestine:
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• Developmentally programmed transcription factors
• Cellular Differentiation
o Cell age and position
• Hormones & Receptors
o Membrane
Kinase phosphorylation pathways
• Nuclear
o Steroid hormone family
o Orphan receptors
• Direct Nutrient effects
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112
What Mechanisms are involved in Gene Expression Regulation
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• Changes in chromatin structure
• DNA methylation (epigenetics)
• Transcriptional activation
o Promoters / Enhancers
• Post-transcriptional modifications
o Alternative splicing
o RNA stability
o Translational effects
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113
Changes in Gene Expression in GI Neoplasia
• Deletion / suppression of specific genes
• Amplification / overexpression of specific genes
• Microsatellite instability (MSI)
• Chromosomal changes
o DNA aneuploidy
o Loss of heterozygosity
• An example of this is seen on the right for gastric adenocarcinoma
traditional Vogelstein adenoma-carcinoma sequence remember genes above: APC is an early change, followed by k-RAS, then DCC and finally p53.
• Second image: must be able to identify the type of instability: chromosomal instability (loss of heterozygosity), DNA mismatch defect (MSI - can be sporadic or hereditary), CpG island methylator-type (loss of MLH1), base excision repair (MYH defect)
114
Prognostic and Predictive Markers in CRC
PROGNOSTIC
APC - 80-100% lifetime risk
MLH1, MSH2, MSH6 - 40-80% lifetime risk
MLH1 methylation-associated silencing - indicative of better prognosis in the absense of adjuvant chemo
18q loss of heterozygosity - poorer outcome
PREDICTIVE
KRAS - pts with activating mutations in KRAS have no response to EGRF-inhibitor therapy
BRAF and V600E - no response to EGRF-inhibitor therapy
MLH1 methylation-associated silencing - may not respond to fluorouracil and may have improved response to irinotecan-containing regimens
115
Role of Transcription Factors in Gene Expression
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• Zn-finger (due to structure [looks like to fingers joined together at base by zinc molecules])
o Steroid hormone family
o Glucocorticoid
o Thyroid
o Vitamin D
o Retinoid, RAR, RXR, etc.
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• Orphan receptors
o HNF4
o FXR
o PPAR-γ, -d
o Krüppel Like Factors
o GATA-4, -5, -6
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• Homeobox factors
o Hox
o Para-Hox
o Cdx2, Cdx1, Pdx-1. etc.
o HNF1
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• Others
o C/EBPα
o Winged helix factors
o Fork head homologue 6, 11
o HNF3
o Sp1, Sp3
o c-Fos, c-Jun
o TCF/SOX
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Olsen et al, Am J Physiol, 2012 – Intestinal Differentiation (transcription factors and migration of cells in crypts)
116
HOX Genes in CRC
• Hox (homeobox) and Parahox gene clusters are organised in increasing numbers from anterior to posterior with low numbers caudal and high numbers rostral
• CDX1 and 2 are the intestine-specific Hox genes (CDX = caudal)
• Roles in development
o Patterns of expression
Segmental
Developmental
o Key roles in the determination of regional cellular differentiation
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• Activation of gene transcription
o Identification of regulated genes
o DNA-binding sites
TAAT motif as core element
o Co-activator requirements
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* Changes in metaplasia and neoplasia
* Yuasa. Nature Reviews Cancer, 2003 – difference in parahox genes (CDx1 and 2 – Cdx1 is more relevant for large intestine, CDx2 is more relevant for small intestine), PDX1 found in pancreas and duodenum, SOX = gene for stomach and oesophagus
117
Hedgehog Targets in CRC
• Sonic hedgehog/Indian hedgehog
• They bind Patched receptor, leading to activation of Smooth and Glistened
o Cyclopamine also activates Smooth
• Activation of Hedgehog pathways occurs in many tumours
• Barakat et al. Trends in Molecular Medicine, 2010: Tissues where Hedgehog activity is important for normal development and can play a role in their conversion to tumors. This schematic (right) depicts the array of tissues in which Hh supports development and can promote tumorigenesis. Hh signaling is important for tumor initiation and maintenance (red), important for maintenance but not initiation (yellow) or implicated in tumorigenesis but its role is not defined (green).
o As you can see from above in GI tumours its role is predominantly not defined
o May be involved in maintenance of tumour in CRC and pancreatic cancer
• Activation of Hedgehog pathway in many tumours
o Gorlin's syndrome (Patched receptor activation)
skin, skeletal muscle, cerebellar tumours
• Digestive tract (increased SHH / IHH expression) – Berman et al. Nature 2003, Thayer et al. Nature 2003
o Oesophageal
o Stomach
o Pancreatic
o Biliary
o (not colonic)
• Interaction of the Hedgehog, Wnt and BMP4 systems Van der Brink et al. Nat Genet 2004
o IHH in differentiated colonocytes
o Downregulation of Tcf4 & b-catenin
118
APC, Beta-Catenin, Wnt, SOX-9
* APC targets b-Catenin for degradation
* b-Catenin/TCF functions as transcription factor
* Loss of APC increases Wnt pathway activity
* Increased Wnt pathway activity in colorectal and other GI cancer
Activation of Wnt cascade in CRC (mutations in APC or other genes in pathway) Excess unregulated proliferation
• SOX9
o Important intestinal crypt transcription factor
o Increased in CRC cell-lines
o Reduced CDX2 and MUC2 expression
Dkk1 (Dickkopf-1)
• Dkk1 is a secreted Wnt inhibitor
• Transgenic mice created which overexpress Dkk1
o Wnt signals drive proliferation in crypts
• Dkk1 ectopic expression deleteriously affects crypt-villous organisation (Pinto et al, 2003)
• It inhibits Wnt binding to Frizzled (and co-receptor LRP5/6), upstream of where APC inhibits Wnt by binding b-catenin
o Increasing Dkk1 may be beneficial in cancer
o Dkks, especially Dkk2 frequently inactivated by epigenetic mechanisms (methylation) in cancer cell lines and primary tumours (Sato et al, Carcinogenesis, 2007)
Bone Morphogenetic Proteins
• Part of TGF-beta family
o BMP2 in colonocytes
• BMP receptors act via SMAD4 and PTEN
• Mutations in BMPR1A, SMAD4 and PTEN found in
o Juvenile intestinal polyposis syndromes
Not FAP or Peutz-Jegher’s
* BMPs control duplication of stem cells (prevent crypt fission)
* Wnt required for stem cell activation and self-renewal (He et al, Nat Genet 2004)
119
Oesophageal Anatomy
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• Divided into thirds
o Cervical oesophagus
Narrow
o Middle oesophagus
Aorta
Left main bronchus
o Lower oesophagus
GOJ columnar epithelium
Left antrum
• The lower you go, there is increased smooth muscle + reduced skeletal muscle
• IMPORTANT: squamous epithelium lining (as opposed to columnar = stomach)
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120
Pathology – Types of Oesophageal Cancer
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• Squamous cell carcinoma
o Risk factors
Alcohol
Smoking
Male
Poor mouth hygiene (link)
Very hot drinks (link)
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• Adenocarcinoma
o Risk Factors
Acid reflux
Obesity
o Oesophageal adenocarcinoma incidence has increased due to increasing rates of obesity (see right)
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121
Symptoms of Oesophageal Adenocarcinoma
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• Difficulty swallowing (dysphagia)
o Progressive – first solids
• Chest pain
• Weight loss
• Other possible symptoms
o Hoarse voice
o Chronic cough
o Vomiting/ regurgitation
o Aspiration
o Anaemia
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Symptoms can be relatively late sign and this tumour spreads easily.
Tumours spread early depth of invasion is directly correlated with lymph node metastases. Greater than 1mm depth, risk of LN metastases go up to 8%. If greater than 2/3mm it can go up to almost 70%.
122
Treatment for Oesophageal Cancer
Oesophagectomy
• Major surgery
• Approximately 1 week in hospital
• Mortality is small in good centres – 2-5%
• Perioperative morbidity rates of 26-41% - Enzinger PC and Mayer RK NEJM, 2003
• QoL scores return to normal after 9 months – Blazeby JM et al, Cancer, 2000
• Mayo Clinic – n = 359– 107/359 who survived 5 years or more (similar in more recent Norwegian study) – McLarty et al, Thorac Surg, 1997. Symptoms/Complications of oesophagectomy:
o reflux was present 60%
o dumping in 50%
o dysphagia to solid food 25%
o 16% were asymptomatic.
o QOL scores similar to normal population
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PPIs in Chemoprevention of oesophageal cancer
PPI
• Some studies suggest PPIs reduce the risk of developing dysplasia and adenocarcinoma in patients with Barrett’s oesophagus Kastelein F et al, Clin Gastroenterol Hepatol, 2013, Nguyen DM, Gastroenterology, 2010 (looked at NSAIDs, Statins and PPIs)
• Some studies suggest that PPIs have no effect.
• Mechanism of Action suggested:
o PPIs can exert anti-inflammatory effects such as anti-oxidant properties and immunomodulatory effects through their interactions with neutrophils, monocytes, endothelial and epithelial cells.
o PPIs have the ability to prevent adhesion molecule binding in malignant cells and suppress metastasis.
• Complications of PPIs
o Brusselaers et al, BMJ, 2017: 797067 patients involved in a cohort study in Sweden found that there is a 3-fold increase in rate of gastric adenocarcinoma in those on longterm PPI (>180 days) – NOT seen with H2 Blockers
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Aspirin in chemoprevention of oesophageal cancer
• Aspirin inhibit cyclooxygenase (COX) may protect against the development of Barrett's oesophagus/ Barrett’s cancer.
• Barrett's oesophagus exhibits increased expression of COX-2.
• Epidemiological data
o Inhibition of COX-2 has been shown to have antiproliferative and pro-apoptotic effects in Barrett's-associated oesophageal adenocarcinoma cell lines.
o Macfarlane TV, Br J Cancer, 2014 – aspirin and NSAIDs associated with a decrease in risk of oesophageal adenocarcinoma. The protective effect may be greater if combined with a statin.
Masclee GM, BMJ, 2015 – case-control population based study not shown to reduce risk
o The ASPECT trial currently evaluating the efficacy and safety of aspirin and esomeprazole for the prevention of cancer in Barrett's esophagus is being conducted in the UK.
• Complications aspirin has side effects (ulceration, GI bleeding)
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Screening in oesophageal cancer
• Is there sufficient evidence to trial a screening programme? Yes
o Pre-malignant condition – Barrett’s Oesophagus
o Easy to survey
o Acceptable to patients
o Enables to catch any cancer early
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Barrett’s Oesophagus
• Pre-malignant condition that is confirmed by histological diagnosis of intestinal metaplasia (squamous cell columnar cell)
o This is due to contant inflammation
• If this process continues it can become low grade dysplasia high grade dysplasia Invasive adenocarcinoma
• Risk increases with progression through each stage although risk is not as high as previously thought (see table below)
• Risk is highest in patients with HGD (6-10% annual risk) focus is on these patients
SEE TABLE ON 217
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Detection of Oesophagus Dysplasia
* Surveillance – new BSG guidelines, 2013 (Gut) has standardised surveillance [see right]
* Biopsy
* Latest BSG guidance
* Fancy techniques (confocal, autoflourescence, NBI)
Prague Classification of Barrett’s Oesophagus
• Must be measuring from GOJ upwards
• Must measure the circumferential and maximal extent of metaplasia
o In this example, Barrett’s is circumferentially seen up to 2cm above GOJ then it is considered a C2
o In this example, the maximum extent is 5 cm above GOJ, hence M5
o C2M5 Barrett’s oesophagus
BSG Surveillance Guidance
• Must use high resolution endoscopy
• Short segment (<3cm) with no SIM (squamous intestinal metaplasia) on repeat biopsy no surveillance
• Short segment + SIM 3-5 yearly surveillance
• Long segment 2-3 yearly surveillance
Target biopsy + quadrantic biopsies ever 2cm
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Acetowhitening
• Acetowhitening is vinegar
• Tholoor et al, Gastrointestinal Endoscopy, 2014 – retrospective cohort study comparing acetic acid chromoendoscopy (AAC) vs. standardised random biopsy protocol (SBP)
o Characteristics: normal surveillance population (not enriched), n=627 or 972 procedures, 4 endoscopists in each arm (AAC and standard Seattle Protocol), all histologists trained in Barrett’s detection, over 4 years (2008-2012)
o Results: HGD/T1 cancer detected in 30% of SBP vs. 87% in AAC
On per-patient analysis, a 6.5-fold gain in neoplasia detection was seen in the AAC cohort compared with the SBP cohort
On per-biopsy analysis, a 147-fold gain in neoplasia detection was seen in AAC cohort vs SBP
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Maximising Detection of HGD
o Use best endoscope high resolution scope (1x106pixels)
o “You do not detect what you see, you detect what you recognize” recognise flat dysplasia, not just raised nodules
o Perform a systematic survey wash mucosa, empty stomach (prevents reflux), gradual exam of inflated oesophagus from GOJ, deflate oesophagus to reveal stretched abnormalities, pay attention to 12-6 o’clock transition zones, retroflex and pull-up
• Kariyawasam V et al, Gastrointestinal Endoscopy, 2012
o Most cancers occur between 3 o’clock and 6 o’clock region presumably to where contents pool when one lies down [see right]
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Endoscopic Management of Dysplasia
Endoscopic Mucosal Resection (EMR)
• Procedure
o Dysplastic lesion is marked prior to resesction
o Cap is placed on oesophagus
o False polyp created by firing a band, snare placed around the false polyp and cut out
o Step-wise approach repeated to ensure whole lesionis removed
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• Complications
o Major
Bleeding
Perforation
o Minor
Stricture dysphagia
Further lesions develop (usually can be treated with only Halo-RFA)
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Halo Radio-Frequency Ablation
• To ablate residual Barrett’s after a dysplastic nodule is resected
• To ablate flat LGD and HGD (and NDBE in America)
• Procedure
o Balloon electrode (bipolar diathermy) that is sized to fit the oesophagus
o Allows for a precise burn of 0.5-1.0mm only ablates only the mucosa (up to submucosa very superficial)
o Hence no structuring
• Need to rescope patients every 3 months – not a quick fix
• Complications – minimal
o Bleeding
o Chest discomfort
• Current RFA Evidence (see slides for range of study references)
o Safe and effective for BE +/- dysplasia
o Cost-effective
o Durable (5 years) but patients are enrolled on a programme (i.e. patients have to come back to have lesions reassessed every 3 months)
o Reproducible in community practice
o Low rate of buried glands
o Eradication of genetic abnormalities
