GI: Colorectal Cancer

Question 1

What is the most common type of colorectal cancer? In what sequence do these develop?

Answer 1

ADENOCARCINOMA - formed from epithelial cells lining colon or rectum.

Form in adenoma-carcinoma sequence: normal mucosa to colon adenoma (colorectal ‘polyps’) to invasive carcinoma.

Question 2

How long does it take for a colonic adenoma to develop into carcinoma? What percentage of adenomas progress to?

Answer 2

Adenomas can be present 10 yrs before becoming malignant.

Only 10% do so.

Question 3

What is the most common site for spread of metastatic colorectal cancer?

Answer 3

liver (can cause jaundice and hepatomegaly)

Question 4

Name the risk factors for colorectal cancer.

Answer 4

1. age >60 yrs
2. diet: low fibre, high processed meat
3. smoking
4. alcohol
5. IBD, esp. UC
6. history of small bowel cancer, endometrial cancer, breast cancer, ovarian cancer
7. family history

Question 5

Describe 2 inherited genetic mutations predisposing to colorectal cancer.

Answer 5

1. FAMILIAL ADENOMATOUS POLYPOSIS (FAP): mutation and inactivation of adenomatous polyposis coli (APC) gene (tumour suppressor gene), resulting in growth of adenomatous tissue
2. HEREDITARY NON-POLYPOSIS COLORECTAL CANCER (HNPCC): mutation to DNA mismatch repair (MMR) genes resulting in defective DNA repair.

Question 6

Describe the common presentations of left and right sided colon cancer.

Answer 6

Right sided (more advanced on presentation):

• occult bleeding causing iron-deficiency anaemia
• weight loss
• abdominal pain
• mass in RIF

Left sided:

• change in bowel habit
• rectal bleeding
• tenesmus
• mass in LIF/DRE
• weight loss

Question 7

Which investigations would you perform on a Pt with suspected bowel cancer?

Answer 7

1. Bloods
   - FBC: may show microcytic anaemia
   - LFTs: assess metastatic spread to liver
   - coagulation screen: assess metastatic spread to liver
   - group and save: in case of surgery/blood transfusion
2. Imaging
   - Colonoscopy with biopsy (gold standard)
   - Flexible sigmoidoscopy + barium enema or CT colography (Pts with major comorbidities)

Question 8

How would you stage a colon cancer? a rectal cancer?

Answer 8

• CT scan (chest/abdo/pelvis): for distant metastases and local invasion with colon cancer
• MRI rectum: rectal cancers only, to assess depth of invasion (and hence need for pre-operative chemotherapy)

Question 9

Which tumour markers can be used to monitor Pts?

Answer 9

CEA and CA 19-9

Question 10

Describe the curative management for colorectal cancer.

Answer 10

For localised bowel malignancy: REGIONAL COLECTOMY + PRIMARY ANASTAMOSIS or STOMA FORMATION

• caecal or ascending colon tumour: right hemicolectomy
• descending colon tumour: left hemicolectomy
• sigmoid colon tumour: sigmoidcolectomy
• high rectal tumour >5cm from anus: anterior resection
• low rectal tumour: abdominoperineal resection

Question 11

In which type of colorectal cancer is radiotherapy used?

Answer 11

Can be used in rectal cancer (but rarely in colon cancer due to risk of damage to small bowel), most often as neo-adjuvant treatment.

Question 12

How can you relieve bowel obstruction by tumour in palliative patients?

Answer 12

• endoluminal stenting: to relieve acute large bowel obstruction in left-sided tumours
• stoma formation: to relieve acute obstruction

Question 13

Name 4 complications of bowel cancer.

Answer 13

1. bowel obstruction
2. bowel perforation
3. recurrence
4. metastasis

Question 14

What is the prognosis (5 yr survival) of colorectal cancer?

Answer 14

50%