Colorectal Cancer

Question 1

Colorectal cancer is the …. most common cancer in the UK

Answer 1

Fourth

And the second highest mortality of any cancer

Question 2

What type of cancer most commonly occurs?

Answer 2

Adenocarcinoma

Rare types: lymphoma, carcinoid, sarcoma

Question 3

How do most develop?

Answer 3

Via a progression of normal mucosa to colonic adenoma (polyps) to invasive adenocarcinoma = adenocarcinoma in sequence

Question 4

Progression of adenoma to adenocarcinoma occurs in approximately what %?

Answer 4

10% of adenomas

Question 5

What genetic mutations have been implicated in predisposing individuals to colorectal cancer?

Answer 5

Adenomatous polyposis coli (APC) = a tumour suppressor gene- mutation of APC results in growth of adenomatous tissue.
Associated with Familial Adenomatous Polyposis (FAP)

Hereditary nonpolyposis colorectal cancer (HNCC)
A DNA mismatch repair gene - mutation to HNCC leads to defects in DNA repair associated with Lynch syndrome

Question 6

What risk factors are there?

Answer 6

Increasing age > 60
FH
IBD
Low fibre diet 
High processed meat intake
Smoking 
High alcohol intake

Question 7

What common clinical features are associated?

Answer 7

Change in bowel habit
Rectal bleeding 
Weight loss
Abdominal pain 
Iron deficiency anaemia

Question 8

Clinical features can vary slightly depending on site of cancer. What features are associated with right sided cancer?

Answer 8

Abdominal pain
Occult bleeding/ anaemia
Mass in RIF
Often present late

Question 9

What features are associated with left sided cancer?

Answer 9

Rectal bleeding
Change in bowel habit
Tenesmus
Mass in LIF or on PR examination

Question 10

NICE guidance suggests referral if…

Answer 10

> = 40 with unexplained weight loss and abdominal pain
= 50 with unexplained rectal bleeding
= 60 with iron deficiency anaemia or change in bowel habit
Positive occult blood screening test

Question 11

Describe colorectal cancer screening

Answer 11

Every 2 years to men and women aged 60-75
For most of UK a faecal immunochemistry test (FIT) used, superseding faecal occult test
If any sample positive - appointment with specialist nurse and further investigation via colonoscopy

Question 12

Why is the FIT more accurate?

Answer 12

Only picks up human blood, so won’t pick up blood that is due to food eaten

Question 13

How does FIT work?

Answer 13

Uses antibodies that specifically recognise human haemoglobin in stool

Can detect and quantify the amount of human Hb in stool sample

Question 14

What investigations should be done in suspected cases?

Answer 14

FBC - microcytic anaemia
LFTs
Clotting screen
CRP

Tumour marker CEA - not as a diagnostic test, but used to monitor disease progression

Imaging - colonoscopy with biopsy = gold standard for diagnosis

Question 15

Why might a colonoscopy not be suitable for patient and what can be done instead for initial diagnosis?

Answer 15

Frailty and comorbidities

Flexible sigmoidoscopy or CT colonography

Question 16

Once diagnosis made, what other investigations required (mainly for staging)?

Answer 16

CT scan CAP to look for distant mets and local invasion

MRI rectum (rectal cancers only) to assess depth of invasion and potential need for pre op chemotherapy

Question 17

What system is used to stage colorectal cancer?

Answer 17

TNM

Duke’s staging system has been largely superseded but still used at some centres for additional staging detail

Question 18

Describe Duke’s staging system

Answer 18

A - confined beneath muscularis propria - 5 year survival 90%
B - extension through muscularis propria - 65%
C - involvement of regional lymph nodes - 30%
D - distant mets - <10%

Question 19

Describe T in the TNM

Answer 19

T1 - tumour only in inner layer of bowel
T2 - tumour grown into muscle layer of bowel
T3 - tumour grown into outer lining of bowel wall, but not through it
T4a - grown through wall and spread into peritoneum covering the organs
T4b - grown through bowel wall into nearby organs

Question 20

Describe M1a,b,c

Answer 20

M1a - spread to 1 distant organ site e.g liver but not peritoneum
M1b - spread to 2 distant sites but not peritoneum
M1c - spread to peritoneum and may have spread to distant organs