Colorectal Cancer (1*)

Question 1

How common is it in the UK?

What are its risk factors?

How does it present?
→ Which symptom is more common with a left-sided ca.?

Answer 1

➊ 3rd

➋ • Increasing age
• Hereditary syndromes - FAP, Lynch syndrome
• Long-standing (10+ yrs) IBD
• Polyp
• Diet - low fibre, high animal fat/meat/refined carbs

➌ • PR Bleeding
• Change in bowel habit
• Tenesmus
• Weight loss, Anaemia
• Obstruction
→ Anaemia

Question 2

Pathophysiology:
Which pathway do most (70%) cases take?

What is the other pathway?

Answer 2

➊ Chromosomal Instability Pathway (Adenoma-Carcinoma Pathway)
• Normal mucosa → Adenoma → Invasive adenocarcinoma

➋ Microsatellite Instability Pathway (Serrated Pathway)
• Cancer arises from serrated polyps (have a serrated/saw tooth appearance microscopically)

Question 3

What is Familial Adenomatous Polyposis (FAP)?
→ How is it managed?
→ Which type of gene is mutated here?

What is Lynch Syndrome?
→ How is it managed?
→ Which type of gene is mutated here?

Answer 3

➊ Autosomal dominant condition where pts develop 100s of adenomatous polyps, making them virtually guaranteed to develop colorectal ca. by their 20s
→ Prophylactic Panproctocolectomy
→ Tumour suppressor gene (APC)

➋ Hereditary Non-Polyposis Colorectal Cancer (HNPCC) - Autosomal dominant condition that carries a 60% risk of developing colorectal ca. by their 30s
→ Regular endoscopic surveillance
→ Mismatch repair genes (MLH1/MSH2)

N.B. Lynch syndrome also increases the risk of gastric, endometrial and ovarian cancer, therefore most females are advised to have a prophylactic TAH+BSO.

Question 4

Bowel Cancer Screening Programme:
What’s the aim of this?

What does it include?

When should pts be 2-wk referred?

Answer 4

➊ Detects bowel cancer at early stage when easier to treat

➋ FIT test every 2 yrs for pts aged 60-74 yrs
• If +ve, pt is offered a colonoscopy

➌ • 40+ with unexplained weight loss + abdominal pain
• 50+ with unexplained rectal bleeding
• 60+ with IDA or changes in bowel habit
• Proven faecal occult blood on testing

Question 5

Investigations:
What are the 2 types of faecal tests that can be done?
→ How sensitive is it?

What’s the 1st line investigation to do?

What are the other things you can do?

How is Colorectal ca. classified?

Answer 5

➊ • FOB (Faecal Occult Blood)
→ Picks up any type of blood present in stool, therefore will be +ve if the pt eats red meat
• FIT (Faecal Immunochemical Test)
→ Only picks up human blood, as well as inflammation. This makes it very sensitive to bowel cancer (if -ve, you can more/less rule it out)

➋ Colonoscopy

➌ • Bloods - FBC, U&E, LFT, CEA
• MRI for rectal ca.
• Staging CT

N.B. CEA isn’t diagnostic but can be used to monitor therapeutic response to interventions

➍ Dukes Criteria:
• A - limited to the bowel wall (i.e. not beyond the muscularis) - 5 yr survival 90%
• B - extending through the bowel wall (i.e. beyond the muscularis) - 5 yr survival 75%
• C - lymph node involvement - 5 yr survival 35-60%
• D - distant metastasis - 5 yr survival <10%

Question 6

How is it managed?

Answer 6

Surgery +/- adjuvant chemoradiotherapy