Colorectal cancer

Question 1

What is colorectal cancer?

Answer 1

• The majority of colorectal cancers are adenocarcinomas derived from epithelial cells.
• About 71% of new colorectal cancers arise in the colon
• 29% in the rectum

Question 2

What is the biggest risk factor for colorectal cancer?

Answer 2

Increasing age

Question 3

Causes of colorectal cancer

Answer 3

A complex interaction of genetic and environmental factors.

• FHx is the most common risk factor after age
• More sporadic
• Obesity confers a 1.5 increased risk

Question 4

Pathophysiology of colorectal cancer

Answer 4

• Colorectal cancers arise from dysplastic adenomatous polyps in the majority of cases.
• A multistep process involving inactivation of tumour-suppressor and activation of oncogenes.
• A single germline mutation in the APC tumour suppressor gene is responsible for the dominantly inherited syndrome familial adenomatous polyposis.
• Metastatic spread usually to liver and lung, less commonly to bone and brain

Question 5

Staging systems used to stage colorectal cancer

Answer 5

TNM staging

Duke’s staging system

Question 6

The Duke’s staging system

Answer 6

Dukes’ A- The cancer is in the inner lining of the bowel. Or it is slightly growing into the muscle layer.
Dukes’ B- cancer has grown through the muscle layer of the bowel.
Dukes’ C- cancer has spread to at least 1 lymph node close to the bowel.
Dukes’ D- cancer has spread to another part of the body, such as the liver, lungs or bones. In the number staging system, this is the same as stage 4. It is also called advanced bowel cancer.

Question 7

Signs and symptoms of colorectal cancer

Answer 7

Increasing age 
Rectal bleeding 
Changes in bowel habit 
Rectal mass
Abdominal mass 
Anaemia 
Abdominal pain (uncommon) 
Weight loss and anorexia (uncommon) 
Abdominal distension (uncommon) 
Palpable lymph nodes (uncommon)

Question 8

Risk factors for colorectal cancer

Answer 8

Increasing age 
Lynch syndrome 
Harmartomatous polyposis syndromes
IBD
APC mutation
MYH associated polyposis 
Obesity

Question 9

Investigations for colorectal cancer

Answer 9

FBC (anaemia) 
Liver biochemistry (normal) 
U&Es (normal) 
Double-contrast barium enema (mass lesion in the colon) 
CT colonography 
Colonoscopy (lesion may be found) 
CT scan of thorax, abdomen and pelvis

Question 10

Differentials of colorectal cancer

Answer 10

IBS 
UC 
Anal fissure 
Crohn's disease 
Haemorrhoids 
Diverticular disease

Question 11

Management of colorectal cancer

Answer 11

Surgery

Chemotherapy if extensive disease