Colorectal cancer and screening Flashcards by Michael Alcorn

How many people die from colorectal cancer per year in the UK

17,000 per year

(second biggest cancer killer in western world)

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What histological type of cancer does colorectal cancer tend to be?

Adenocarcinoma (95%)

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Describe the role of genetics as a risk factor for colorectal cancer

85% of CRC is sporadic and has no link to genetics

10% of patients have a ‘familial risk’

Inheritible predisposing conditions such as mutated HNPCC, FAP account for 5%

1% caused by IBD

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What are the risk factors for CRC?

Old age

Male

Previous adenoma/CRC

Previous IBD

Poor diet / obesity / Lack of exercise

Smoking

Diabetes

Family history

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Most colorectal cancers begin as _______

Polyps (adenomas)

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What are the main histological types of polyp (adenoma)?

Tubular (75%)

Indeterminate tubulovillous (15%)

Villous (10%)

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What is the difference between a pedunculated and sessile polyp?

Pedunculated - polyp has a connective tissue stalk

Sessile - no stalk

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What dietary factors can increase the risk of CRC?

Low Fibre, fruit & veg and calcium

High red meat and alcohol

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What changes occur that allow adenomas to become carcinomas (cancerous)?

Activation of oncogene

Loss of tumour suppressor gene

Defective DNA pathway repair genes - microsatellite instability

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Give examples of oncogenes that can be activated to allow CRC to develop

k-ras

c-myc

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Give examples of tumour suppressor genes

APC

p53

DCC

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What are the main symptoms of Colorectal cancer?

Rectal bleeding

Change in bowel habit - looser and more frequent stools

^{<em>For above^: if 1 then investigate > 60s, if both then investigate > 40</em> <em>year olds</em>}

Tenesmus - urge to defecate / rectal fullness

Symptoms of anaemia (iron deficiency): lethargy, breathlessness etc

Weight loss

Systemic symptoms: Weight loss, anorexia

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Cancers in the caecum and right colon are often asymptomatic until they present as _________

Often asymptomatic until they present as iron deficiency anaemia

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What are the main signs of Colorectal cancer?

Rectal or abdominal mass may be palpable

Iron deficiency anaemia

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How can colorectal cancer present as an emergency?

Can cause acute colonic obstruction if the tumour is stenosing

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What is the primary investigation for CRC?

Colonoscopy - gold standard

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What are the benefits and problems with colonoscopies?

Pros:

Good view
Biopsies (mandatory)
Can be used therapeutically (polypectomy)

Cons:

Requires sedation
Risk of perforation, bleeding etc

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What radiological imaging can be used to investigate CRC?

CT colonography - gives 3D virtual colonoscopy (good for visuals)

Barium enema

CT abdo/pelvis

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What investigations are done to stage CRC?

CT scan: Chest, abdo, pelvis

MRI scan for Rectal tumours

PET scan / rectal endoscopic ultrasound (in some cases) - _{i think these are done if to look at anything suspicious (metastasis) on the CT/MRI}

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What staging system is used in CRC?

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Dukes’ staging system (which uses TNM)

What is the treatment approach to CRC?

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Surgery used in about 80% of cases

Adjuvant postoperative chemotherapy often used (more later)

Radiotherapy is only useful in rectal cancer

Palliative: Chemo and stenting are options

What is Dukes A CRC and how is it treated?

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A = tumour confined to the mucosa

Treated using endoscopic or local resection

(same with polyps)

How are more advanced cancers treated?

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Operative procedure variable - depending on site, stage and size of tumour

Surgery tends to be laparoscopically but can be done as laparotomy

Some patients require colostomy - stoma formation may be temporary/permanent

Palliative: Chemotherapy, colonic stenting

When is chemotherapy indicated for use?

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Dukes C / sometimes Dukes B

Used adjuvantly (postoperative)

Used if there is positive lymph node histology as it is useful fo ‘mopping up’ micrometastasis

What main chemo agent are used for adjuvant treatment of CRC?

**5-FU** (fluorouracil) +/- others but we dont care about that

When is radiotherapy indicated?

**Rectal cancer only** Is used **Neoadjuvantly** (before surgery) **+/- chemotherapy** to control primary tumour prior to surgery

Why is stenting used in palliative care for CRC?

To prevent **colonic obstruction** (large bowel obstruction) To improve patients remaining time as much as possible

What is the prognosis for each Dukes stage? ^{(ignore the photo if the answers are different)}

**A - 83%** 5 year survival **B - 64%**" **C - 38%**" **D - 3%**"

What lifestyle advice should be given to patients to reduce their chances of developing CRC?

30 mins **physical activity** on most days **BMI** 18.5-25.0 kg/m² 5 or more portions **fruit and veg** Dont smoke / quit **smoking**

What is the aim of population screening for CRC?

Detect pre-malignant / early cancers in the general population

What modalities are used for screening for CRC?

Faecal occult blood test (FOBT) Faecal immunochemical test (FIT) Flexible sigmoidoscopy Colonoscopy CT colonography

What is the scottish screening programme for CRC in 2007?

50-74 year olds FOBT every 2 years If FOBT positive then receive colonoscopy

What test is currently being used in scotland (as of 2017) to screen for CRC and what are it's advantages?

**Faecal immunochemical testing (FIT)** Automated, quantitive and more user friendly than FOBT

What high risk groups are screened for CRC?

Those with **Heritable conditions:** * *FAP (familial adenomatous polyposis)* * *HNPCC (hereditary non-polyposis colorectal cancer)* **Inflammatory bowel disease** **Familial risk** **Previous adenomas / colorectal cancers**

What is FAP?

**Familial adenomatous polyposis** **Autosomal dominant** condition in which the epithelium of the colon becomes covered in adenomas (polyps) Caused by **mutation of APC gene on chromosome 5**

How are FAP patients managed?

Screening - **annual colonoscopy** from ages 10-12 up **Prophylactic proctocolectomy** usually at age 16-25 years old

What are the extracolonic manifestations of FAP?

Benign gastric fundic cystic hyperplastic (not a clue what this is meaning) Duodenal adenomas in 90% with periampullary cancer in around 5% (surveillence endoscopy) Desmoid tumours (10-20%) - noncancerous CT growths CHRPE - congenital retinal hypertrophy of the pigment epithelia

What drugs group can be used to help patients with FAP and how?

Some NSAIDs work as chemoprevention E.g. Sulindac reduces polyp number and prevents recurrence of high grade adenomas in the retained segment after a proctectomy

What is HNPCC?

Hereditary nonpolyposis colorectal cancer (HNPCC) - most common form of hereditary colorectal cancer Autosomal dominant syndrome - defective mismatch repair (MMR) proteins: * MLH1 * MSH2 HNPCC, accounts for 2-5% of all colorectal carcinomas

What is different about HNPCC tumurs compared to other tumours?

Typically have molecular characteristic called **microsatellite instability** *(frequent mutations in short repeated DNA sequences (microsatellites))*

How would a patient with HNPCC present with cancer?

Early onset colorectal cancer which tends to be right sided (Ascending colon) May have cancer in other sites: endometrial, genitourinary, stomach, pancreas

How is HNPCC diagnosed and managed?

Diagnosed through genetic testing - clinical criteria (Amsterdam / Bethesda) Screening from age 25: colonoscopy every 2 years

How are patientsd with a familial risk of CRC screened?

CRC in 3 FDRs with mean age \<60 - -\> High moderate risk - -\> 5 yrly colonoscopy from age 50 CRC in 2 FDRs over 60 or in 1 FDR \<50 - -\> Low Moderate Risk - -\> One Colonoscopy at age 55

How is CRC screened for in patients with IBD?

A surveillance colonoscopy 10yrs post diagnosis Then further investigations dependant on duration, extent, dysplasia and activity of the IBD

How often are patients with a history of CRC screened and how?

Colonoscopy every 5 years

What determines the screening programme for patients with previous adenomas?

Dependant on number of polyps, size and degree of dysplasia

What new investigations are surfacing for screening/detection of CRC Why are these good?

Faecal haemoglobin testing - could be a good 'rule out test' for significant bowel disease and would avoid unnecessary colonoscopy

Summarise the primary care investigation for a patient suspicious for CRC (before imaging n all that shite)

Full blood count U+E's FIT test (stool test)

Colorectal cancer and screening Flashcards

(49 cards)