Colorectal Cancer + Screening

Question 1

What is the role of screening as applied to colon cancer and how is it conducted?

Answer 1

Screening for colorectal cancer is designed to cover:

• Average risk population
• High risk groups

Aims:

• Detect pre-malignant adenomas/early cancers in the general population

Modalities of screening:

• Faecal occult blood test
• Faecal immunochemical test
• Flexible sigmoidoscopy
• Clonoscopy
• CT Colonography

Question 2

How is colorectal cancer staged?

Answer 2

Investigations:

• CT scan chest/abdo/pelvis
• MRI scan for rectal tumours
• PET scan in selected cases

TNM Staging:

T1-4 = local disease

N0-N1 = lymph node involvement

M0-M1 = Distant metastases

Duke’s Classification:

A – Tumour confined to mucosa

B – Tumour extended through mucosa to muscle layer

C – Involvement of lymph nodes

D - Distant metastatic spread

Question 3

How is colorectal cancer treated?

Answer 3

1) Surgery:

Dukes A and polyps = Endoscopic or local resection

Operative procedure depends on site, size and stage of tumour

Laparotomy (more invasive) vs. laparoscopy (less invasive)

May require stoma permanently or temporarily

Removal of lymph nodes for histological analysis

2) Chemotherapy:

Dukes C

+ve Lymph node involvement

Adjuvant (after main therapy)

3) Radiotherapy:

Only rectal cancer

Neoadjuvant (before main therapy) +- chemo

4) Palliative care

For advanced disease

Question 4

What is the prognosis for colorectal cancer?

Answer 4

A - 83% 5 year survival

B - 64% 5 year survival

C - 38% 5 year survival

D - 3% 5 year survival

Question 5

What are the key point of the Scottish Bowel Screening Programme?

Answer 5

Age - 50-74

FOBT - every 2 years (if+ve = colonoscopy)

15% reduction in relative risk of colorectal cancer mortality

Question 6

How does the screening programme differ for high risk patients?

Answer 6

High risk groups:

FAP (Familial adenomatous polyposis):

1) Most with this APC gene mutation go on to have polyps by age 35
2) There is then a high risk of malignant change by age 40 if left untreated
3) Annual screening colonoscopy from age 10-12
4) Prophylactic proctocolectomy (remove rectum and part of colon) from age 16-25

HNPCC (Hereditary Nonpolyposis Colorectal Cancer):

1) MLH1 + MSH2 genes affected
2) Screening started from age 25 with a 2 yearly colonoscopy

Previous CRC = 5 yearly colonoscopy