Colorectal carcinoma

Question 1

What is colorectal carcinoma?

Answer 1

Colorectal carcinoma = malignant tumours of the large bowel

Types
Majority = adenoma carcinoma (epithelial derived)
Carcinoid tumours
GI stromal cell tumours

Location
71% = colon (30% = sigmoid colon, 15-20% = ascending colon, 20% = transverse and descending colon)
29% = rectum

Question 2

What is the aetiology of colorectial carcinoma?

Answer 2

Environmental and genetic factors

A sequence from epithelial dysplasia -> adenoma -> carcinoma is thought to occur, involving the accumulation of genetic changes in oncogenes and TS genes

Oncogenes = APC, K-ras, TS genes = p57, DCC

Some inherited conditions are associated with high rates of colorectal carcinoma
Chronic bowel inflammation (e.g. IBD) are increases the risk

Question 3

What are the risk factors for colorectal carcinoma?

Answer 3

Old age (Rare before 40)

APC mutation
Lynch syndrome = HNPCC (hereditary non-polyposis colorectal cancer) - Autosomal dominant
Increased risk of developing CRC at an early age (mean = 44 years)

IBD

Obesity

Acromegaly

Lack of dietary fibre

Question 4

What is the epidemiology of colorectal carcinoma?

Answer 4

Third most common cancer in the Western world
Second most common cause of cancer death in the West (20,000 deaths/year)

Highest incidence in Europe and North America
Lifetime risk is 5%
Average age of diagnosis is 70

Question 5

What are the symptoms of colorectal carcinoma?

Answer 5

LHS colon/rectum
Change in bowel habit (usually increased frequency/looser)
Rectal bleeding
Blood/mucous mixed in with stool
Tenesmus
Weight loss

RHS colon – later presentation
Anaemia (90%)
Weight loss
Non-specific malaise

As an emergency (20%)
Large bowel obstruction - Abdominal pain, Distension
Perforation - Haemorrhage, Peritonitis

Question 6

What are the signs of colorectal carcinoma?

Answer 6

Anaemia (RHS)
Abdominal mass/rectal mass on DRE

Metastatic disease - Hepatomegaly, Shifting dullness, Lymphadenopathy, Distention

Question 7

What are appropriate investigations for colorectal carcinoma?

Answer 7

Bloods
FBC: microcytic anaemia
LFTs: often normal
Tumour markers: CEA (carcinoembryonic antigen)

Monitor response, disease reoccurrence
Colonoscopy/Sigmoidoscopy

Visualisation and biopsy
Polypectomy
Stool sample - FOB
Barium contrast - Apple-core stricture

Abdo US - Hepatic metastases
CT - Colonic wall thickening, Enlarged lymph nodes, Liver metastases/Ascites, Staging