Colorectal cancer and screening Flashcards
How many people die from colorectal cancer per year in the UK
17,000 per year
(second biggest cancer killer in western world)
What histological type of cancer does colorectal cancer tend to be?
Adenocarcinoma (95%)
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
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
Most colorectal cancers begin as _______
Polyps (adenomas)
What are the main histological types of polyp (adenoma)?
Tubular (75%)
Indeterminate tubulovillous (15%)
Villous (10%)
What is the difference between a pedunculated and sessile polyp?
Pedunculated - polyp has a connective tissue stalk
Sessile - no stalk
What dietary factors can increase the risk of CRC?
Low Fibre, fruit & veg and calcium
High red meat and alcohol
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
Give examples of oncogenes that can be activated to allow CRC to develop
k-ras
c-myc
Give examples of tumour suppressor genes
APC
p53
DCC
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
Cancers in the caecum and right colon are often asymptomatic until they present as _________
Often asymptomatic until they present as iron deficiency anaemia
What are the main signs of Colorectal cancer?
Rectal or abdominal mass may be palpable
Iron deficiency anaemia
How can colorectal cancer present as an emergency?
Can cause acute colonic obstruction if the tumour is stenosing
What is the primary investigation for CRC?
Colonoscopy - gold standard
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
What radiological imaging can be used to investigate CRC?
CT colonography - gives 3D virtual colonoscopy (good for visuals)
Barium enema
CT abdo/pelvis
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
What staging system is used in CRC?
Dukes’ staging system (which uses TNM)
What is the treatment approach to CRC?
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?
A = tumour confined to the mucosa
Treated using endoscopic or local resection
(same with polyps)
How are more advanced cancers treated?
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?
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)
