Colorectal Carcinoma

Question 1

How common is colorectal cancer?

Answer 1

3rd most common malignancy

Question 2

Which is more common colon or rectal?

Answer 2

Colon x1.5 more common than rectal

Question 3

What are the risk factors for colorectal cancer?

Answer 3

• Diet: Low fibre, high red meat & fat
• Inflammatory disease: UC related to extent of involvement
• Familial: FAP, HNPCC, Gardner’s syndrome

Question 4

What is the pathophysiology of colorectal cancer?

Answer 4

Normal epithelium to hyper proliferative epithelium, benign adenoma then invasive carcinoma
Stepwise accumulation of defects
APC mutations: Benign adenomas but more mutations needed for invasive carcinoma formation

Question 5

What is the histology of colorectal cancer?

Answer 5

Epithelial: Adenocarcinoma MOST COMMON
Carcinoid
SCC & adenosquamous carcinoma
GI stromal
Primary malignant lymphoma

Question 6

Where do tumours in the bowel arise?

Answer 6

40% of L.bowel occur in the rectum
20% Sigmoid colon
6% Caecum
90-95% adenocarcinomas

Question 7

How do colorectal cancers spread?

Answer 7

Local invasion
Lymphatics
Venous
Coelomic spread

Question 8

How do colorectal cancers present?

Answer 8

Altered bowel habits
Weight loss
Rectal bleeding
Vague abdo pain
Iron deficiency anaemia: Right sided tumours & caecum

Question 9

What investigations should be done for colorectal cancer?

Answer 9

Rectal Ex
Right sigmoidoscopy
Flexible sigmoidoscopy
Colonoscopy (allows biopsy)
Double contrast barium enema (less useful as no histology)
CT for staging
CEA markers

Question 10

How is surgery in colorectal cancer used?

Answer 10

• Radical resection for primary colorectal carcinoma,
• Advanced disease: resect liver mets & primary
• Palliative: Surgery or stenting to manage/prevent an obstructing lesion

Question 11

How is radiotherapy used in colorectal cancer treatment?

Answer 11

• Treat rectal carcinomas
• Pre-op/adjuvant in high risk rectal carcinomas before/after total resection
• Palliative: Local recurrences, bone mets

Question 12

Why is RT not commonly used for colon cancers?

Answer 12

Toxicity to adjacent organs

Question 13

How is chemo used for colorectal cancer?

Answer 13

• Adjuvant: High risk colorectal carcinomas

- Duke’s C= 6months adjuvant Tx

Question 14

What is the prognosis using Duke’s stage A & D at 5years?

Answer 14

A= 80%
D=5%
<40years= poor prognosis reflecting more aggressive tumour