Colorectal Cancer

Question 1

What is colorectal cancer?

Answer 1

Malignant adenocarcinoma of the large bowel

Question 2

Describe the distribution of colorectal cancer

Answer 2

Distribution:
60%: rectum + sigmoid
30%: ascending colon
10%: rest of colon

Question 3

Describe Dukes Classification of colorectal cancer, giving 5yr survival rates

Answer 3

A: limited to muscularis mucosae, 93%
B: extension through muscularis mucosae, 77%
C: involvement of regional lymph nodes, 48%
D: distant metastases, 6.6%

Question 4

Describe the aetiology of colorectal cancer

Answer 4

Environmental + genetic
Sequence of genetic changes (e.g. APC then COX2 over-expression then K-Ras then p53) from epithelial dysplasia to adenoma to carcinoma, involving accumulation of genetic changes in oncogenes + TSGs.

Question 5

Describe the epidemiology of colorectal cancer

Answer 5

2nd MOST COMMON cause of cancer death in the West
3rd most common cancer
UK: 20,000 deaths per year
Average age: 60-65 yrs

Question 6

List 8 risk factors for colorectal cancer

Answer 6

Western diet (e.g. red meat, alcohol, low fibre) 
Obesity  
Colorectal polyps  
Previous colorectal cancer 
Family history  
IBD (UC > crohns) 
Alcohol 
Smoking

Question 7

What do symptoms of colon cancer depend upon?

Answer 7

size + location of the tumour

Question 8

List 3 signs of colorectal cancer

Answer 8

Anaemia, esp. in R-sided
Abdominal mass
Low-lying rectal tumours may be palpable on DRE

Question 9

List 4 symptoms of left sided colon/ rectal cancer

Answer 9

Change in bowel habit
Rectal bleeding (blood or mucus mixed with the stools)
Tenesmus (due to space-occupying tumour in rectum)
Mass PR in 40-80% in rectal carcinomas

Question 10

List 6 features/ symptoms of right sided colon cancer

Answer 10

Presents later 
Anaemia symptoms (lethargy) 
Weight loss  
Non-specific malaise  
Lower abdominal pain (rare)  
Abdo distention in advanced disease due to ascites or intestinal obstruction

Question 11

What is tenesmus?

Answer 11

sensation of incomplete emptying after defecation

Question 12

Name 2 genetic conditions associated with high rates of colorectal carcinoma

Answer 12

Familial adenomatous polyposis (FAP)
Lynch Syndrome (HNPCC)

Question 13

What bloods should be taken in colon cancer?

Answer 13

FBC: anaemia  
LFTs + renal function (baseline): usually norm even with liver mets  
Tumour markers (CEA): only measured on confirmation of dx

Question 14

What stool based test is used in identifying colon cancer?

Answer 14

FOBT: screening test from 60-74yr every 2yrs ~10% of positive FOBT have bowel cancer detected at colonoscopy

Question 15

What invasive investigations are performed for colorectal cancer?

Answer 15

Sigmoidoscopy

Colonoscopy: GOLD STANDARD: can biopsy tumour: confirms dx with characteristic pathological appearance

Question 16

What investigations may be performed for visual inspection in colorectal cancer?

Answer 16

Double-Contrast Barium Enema: May show ‘apple core’ strictures
CT colonography (virtual colonoscopy)
Contrast CT TAP: For staging (Duke’s staging)

Question 17

What tumour marker is associated with colorectal cancer? What is the main purpose of measuring this?

Answer 17

CEA

to detect relapse of cancer after surgical tx + evaluation of chemo

Question 18

20% of colorectal tumours will present as an EMERGENCY with pain and distension. What is this due to?

Answer 18

Large bowel obstruction

Haemorrhage or peritonitis due to perforation

Question 19

Give 2 signs that may be present when colorectal cancer has become metastatic

Answer 19

Hepatomegaly (lungs, liver + lymph N are likely)

Ascites

Question 20

Cancers in which area would cause change in bowel habit with no rectal bleeding? What investigations should be performed in an over 60 year old with this presentation?

Answer 20

Ascending or transverse colon

Full colonoscopy

Question 21

Why is obstruction and thus tenesmus more likely to occur in left sided colon/ rectal cancers?

Answer 21

Diameter is smaller on the left side + bowel content more solid.