1: Colorectal Cancer Flashcards
How common is colorectal cancer
Third most common UK cancer
How does incidence of colorectal cancer change
Increases with age.
Familial associated colorectal cancer may occur at a younger age.
How do the majority of colorectal cancers develop
adenoma-carcinoma sequence
Explain adenoma-carcinoma sequence
normal mucosa evolves to colonic adenoma (polyp) then progresses to invasive adenocarcinoma
what percentage of adenomas progress to adenocarcinomas
10%
What are two genetic syndromes that lead to colorectal cancer
HNPCC (Lynch)
Familial Adenomatous Polyposis
What gene is mutated in familial adenomatous polyposis
APC
What type of gene is APC
Tumour suppressor gene
What is Lynch syndrome also called
HNPCC
What genes are mutated in Lynch syndrome
DNA mismatch repair genes: MLH1 and MSH2
In HNPCC which side of the colon are tumours more likely to be
Right
What criteria is used to diagnose to identify lynch syndrome
Amsterdam
What is the amsterdam criteria for Lynch syndrome
3 Family members (one first generation)
2 Successive generations
1 Family member under 50-years
What are 5 risk factors for colorectal cancer
Age FH IBD Low Fibre Diet High processed meat intake Smoking Alcohol
How do symptoms of colorectal cancer vary
Depending on location
What are 5 symptoms of left-sided colorectal cancer
- Change bowel habbit
- Rectal bleeding
- Tenesmus
- Mass LIF
- Mass on PR
What are 3 symptoms of right-sided colorectal cancer
- Abdominal pain
- Occult bleed
- Mass in RIF
How may colorectal bleeding on either side present
- Change bowel habit
- Rectal bleed
- Weight loss
- Abdominal pain
- IDA
When should individuals >40y be sent for urgent investigation for bowel cancer
Unexplained weight loss
When should individuals >50y be sent for urgent investigation for bowel cancer
Rectal Bleeding
When should individuals >60y be sent for urgent investigation for bowel cancer
IDA
Or, change bowel habit
When should any individual be sent for bowel cancer assessment
+ve faecal occult blood test
When should a 2W referral for bowel cancer be made
If individuals have
- Abdominal mass
- Or, anal mass
- Or, <50 with rectal bleeding
AND one of:
a. abdominal pain
b. change bowel habit
c. weight loss
d. IDA
What type of cancer are colorectal cancers
adenocarcinomas
Where do 40% of colorectal cancers arise
rectum
Where do 30% of colorectal cancers arise
sigmoid colon
What stool test is ordered for colorectal cancer and what will it show
Faecal occult blood test - shows presence blood in stool
What blood tests are ordered in colorectal cancer
FBC
CEA
What will FBC show in colorectal cancer
microcytic anaemia (IDA) - especially if right-sided
What is CEA used for in colorectal cancer
it is not diagnostic! but used to monitor response to treatment
What is first-line imaging for colorectal cancer
colonoscopy and biopsy = gold-standard
If a patient has several co-morbidities what is used as an alternative to colonoscopy
flexible sigmoidoscopy and barium enema
What sign will be present on barium enema in colorectal cancer
apple core sign = construction lumen due to colorectal cancer
What imaging is used to stage the disease
CT CAP
Why may MRI be used in colorectal cancer
Assess risk of local recurrence
When is endo-anal US used in colorectal cancer
Asses depth invasion of rectal cancers
How is colorectal cancer staged
TNM Staging
What was used previously to stage colorectal cancer
Duke’s staging
What is Duke’s stage A
Confined to mucosa
What is Duke’s stage B1
Extending to muscularis propria
No node involvement
What is Duke’s stage B2
Penetrating through muscularis propria
No node involvement
What is Duke’s stage C1
Extending to muscularis propria
Node involvement
What is Duke’s stage C2
Penetrating through muscularis propria
Node involvement
What is Duke’s stage D
Metastses
What is the survival rate of Duke’s stage A
90
What is the survival rate of Duke’s stage B
65
What is the survival rate of Duke’s stage C
30
What is the survival rate of Duke’s stage D
10
Explain screening for bowel cancer
- 55y = offered one-off flexible sigmoidoscopy
- 65-74 = offered FIT every 2-years
- > 75 = can request FIT every 2-years
If faecal immunochemical testing is positive what are individuals offered
Colonoscope
What is the aim of surgical intervention for bowel cancer
To remove location where tumour is (regional colectomy)
What surgery will someone with ascending or caecal tumour receive
Right hemi-colectomy
What surgery will someone with tumour in transverse colon receive
Extended right hemi-colectomy
What surgery will someone with descending colon cancer receive
Left hemicolectomy
What surgery will someone with sigmoid tumour receive
Sigmoidectomy
What are indications for anterior resection
High anal tumour:
- >5cm from anal sphincter
What is the advantage of anterior resection over AP resection
Anal sphincter remains intact
When is abdominalperineal resection indicated
Low anal tumour:
<5cm from anus
What does AP resection involve
Remove:
Distal colon
Rectum
Anal sphincter
What does AP resection result in
Removal anal sphincter and permanent colostomy
What is a Hartmann procedure indicated for
Emergency bowel obstruction
What does a Hartmann procedure involve
Remove recto-sigmoid junction. Attach a colostomy and form a rectal stump.
When is chemotherapy indicated for colorectal cancer
metastatic disease
Why is radiotherapy not used for colon cancer
Damages the small bowel
When may radiotherapy be used
Adjuvant rectal cancers
What is used for palliation of colorectal cancer
- Endoluminal stenting = if obstruction - often left-side
- Stoma formation
