Colorectal carcinoma

Question 1

Where does colorectal carcinoma usually arise?

Answer 1

71% arise in the colon, and 29% arise in the rectum.

Question 2

What classification system is used for colorectal carcinomas?

Answer 2

Dukes’ classification.

Question 3

Who is affected?

Answer 3

· More common in males.

· Rare in <40 year olds.

Question 4

What is the pathophysiology of colorectal carcinomas?

Answer 4

· Arise from dysplastic adenomatous polyps.

· Inactivation of tumour suppressor and DNA repair genes, and activation of oncogenes:
- This confers a selective growth advantage to the colonic epithelial cell and drives the transformation from normal colonic epithelium to adenomatous polyp to invasive CRC.

· FAP - A single germline mutation in the APC tumour suppressor gene.

· Spread is to local lymph nodes via enteric venous drainage to the liver and haematogenously to the lungs, and less commonly to the bone and brain.

Question 5

What are the risk factors for colorectal cancer?

Answer 5

· Increasing age. 
· APC mutation. 
· Lynch syndrome (HNPCC).
· IBD. 
· Obesity.

Question 6

What are the signs and symptoms of colorectal cancer?

Answer 6

· Rectal bleeding.
· Change in bowel habit.
· Rectal mass.
· Anaemia.

Question 7

What investigations would you request if you suspected a patient had colorectal cancer?

Answer 7

· FBC.
· LFTs.
· Renal function. 
· Colonoscopy. 
· Double-contrast barium enema. 
· CT.

Question 8

Suggest some differential diagnoses.

Answer 8

· IBS. 
· UC. 
· Crohn's. 
· Haemorrhoids.
· Anal fissure.
· Diverticular disease.

Question 9

What treatment options are available for colorectal cancer?

Answer 9

Treatments depend on if suitable for surgery or not, rectal cancer, colon cancer and staging. They include:
· Local or radical excision.
· Radical resection.
· Preoperative/ Postoperative radiotherapy /chemotherapy.
· Stenting.
· Monoclonal antibodies.

Question 10

What complications can occur?

Answer 10

· Bone marrow suppression during chemotherapy - Neutropenia, Thrombocytopenia and Anaemia.

· Oxaliplatin-associated hepatotoxicity and/or neuropathy.

· Chemo-associated GI symptoms.

· Chemo-associated alopecia.

· Radiotherapy-associated faecal incontinence (rectal cancer).