Pathology of colorectal cancer

Question 1

How common is colorectal cancer in the UK?

Answer 1

3rd most common cancer

Question 2

What type of cancers are most colorectal cancers?

Answer 2

Adenocarcinomas

Question 3

86% of colorectal cancers present in those aged over what? and rarely below the age of what?

Answer 3

60

rarely below the age of 40

Question 4

Is the incidence of CRC higher in men or women?

Answer 4

Men

Question 5

Where in the world are there relatively low & high rates of CRC?

Answer 5

Africa and Asia - low

New Zealands, Western Europe and North America - high.

Question 6

Are the rates of incidence for CRC increasing or decreasing? What is happening to mortality rates?

Answer 6

Incidence is increasing (particularly males) BUT

Mortality rates are decreasing

Question 7

What are some predisposing genetic factors for CRC?

Answer 7

• Neoplastic polyps
• IBD
• Familial adenomatous polyposis (FAP)
• Lynch syndrome / HNPCC
• Previous cancers

Question 8

What are some environmental risk factors for CRC?

Answer 8

Obesity increases risk and mortality from CRC
Diet low in fibre and high in red processed meats
High alcohol intake
Smoking

Question 9

65-80% of colorectal cancers are what?

Answer 9

Sporadic cases

Question 10

Tests for colorectal cancer?

Answer 10

FBC
Faecal occult blood
Sigmoidoscopy or colonoscopy
LFT, liver MRI/USS
If family hx of FAP - refer for DNA tests

Question 11

What percentage of the older population have polyps in the colon?

Answer 11

60%

Question 12

What is lynch syndrome?

Why do we want to identify those with lynch syndrome?

Answer 12

Sporadic mutation of DNA repair gene meaning DNA damage accumulates resulting in people developing cancers including CRC at a younger ages (usually below 50).
We want to identify these patients as they have a higher risk of developing further cancers (endometrium, ovary, urinary tract, stomach, hepatobiliary, small bowel)

Question 13

What is familial adenomatous polyposis (FAP)?

What percentage of CRC’s are caused by this disorder?

Answer 13

Adenoma caused by mutation in APC tumour suppressor gene causing upregulation of epithelial proliferation (adenoma formation)
Only accounts for 1% of CRC.

Question 14

What percentage of colorectal cancers can be detected with a DRE?

Answer 14

38%

29% occur in the rectum.

Question 15

What is the 5 year survival percentage for a CRC tumour which has been completely excised or not completely excised?

Answer 15

75% 5 year survival - fully excised

20% 5 year survival - not completely excised

Question 16

Describe Dukes staging for CRC.

Answer 16

Dukes A - Cancer is in the inner lining of the bowel (submucosa) or slightly into muscular wall
- 95% 5 year survival

Dukes B - Cancer has grown through the muscle layer of the bowel - majority fall into this category
- 75% 5 year survival

Dukes C - Cancer has spread to at least 1 lymph node close to the bowel
- 35% 5 year survival

Dukes D - Cancer has spread to another part of the body such as liver, lungs or bones (Same as stage 4 = advanced bowel cancer)
- 25% 5 year survival

Question 17

What treatment options are there for colorectal cancer?

Answer 17

Surgery: laproscopic surgery
Radiotherapy: mostly for palliation
Chemotherapy: for stage 3.

Question 18

What is the prognosis like for stage 1 and 4 CRC?

Answer 18

stage 1 - 75% 5 yr survival

stage 4 - 25% 5 year survival