Colorectal Cancer

Question 1

Description: What is colorectal cancer and what fraction of each organ is affected?

Answer 1

Cancer of the colon (2/3) and rectum (1/3)

Question 2

Description: The majority of colorectal cancers are

Answer 2

Adenocarcinomas (95%)

Question 3

Aetiology/Risk Factors: What are the risk factors for colorectal cancer? (4)

Answer 3

• Sporadic
• Familial risk (FAP)
• Inherited conditions (HNPCC)
• Inflammatory Bowel Disease

Question 4

Aetiology/Risk Factors: What are the specific risk factors for sporadic cases of colorectal cancer

Answer 4

• Male
• Age
• Diabetes mellitus
• Smoking
• Previous colorectal cancer
• Obesity
• Lack of exercise

Question 5

Pathology: What can colorectal polyps develop into?

Answer 5

Colorectal cancer

Question 6

Pathology: What are the 3 histological types of colorectal polyps?

Answer 6

3 histological types of colorectal polyps (ADENOMAS):

• Tubular (75%)
• Villous (10%)
• Intermediate tubulovillous (15%)

Question 7

Pathology: Describe the adenoma - carcinoma sequence (i.e how a cell gets from being a benign adenoma to a malignant carcinoma)

Answer 7

To get from adenoma to carcinoma the following processes take place:

• Activation of oncogenes (k-ras and c-myc)
• Loss of tumour suppressor genes (p53, APC and DCC)
• Defective DNA repair pathways (genes that inhibit apoptosis are over-expressed)

Question 8

Symtoms and signs: How does colorectal cancer present?

Answer 8

Presentation of colorectal cancer:

• Rectal bleeding (left)
• Altered bowel opening/habit (left)
• Palpable rectal or right lower abdominal mass
• Iron deficiency anaemia (right)
• Systemic symptoms of malignancy (weight loss and anorexia) (right)
• Tumour (stenosing) causes acute colonic obstruction (left and right)
• Tenesmus (desire to defecate)

Question 9

Investigations: How do we investigate colorectal cancer?

a) To make a diagnosis? (1
(b) Radiological imaging investigations (3)
(c) Staging investigations (3)

Answer 9

(a) To make a diagnosis
Colonoscopy and biopsy

(b) Radiological imaging investigations
- Barium enema
- CT colonography
- CT of the abdomen and pelvis

(c) Staging investigations
- CT of the chest/abdomen/pelvis
- MRI for rectal tumours
- PET scan

Question 10

Investigations: How do we stage colorectal cancer? (2)

Answer 10

• TNM staging

- Dukes’ staging (A, B, C1, C2 and D)

Question 11

Treatment: How do we treat colorectal cancer?

a) Procedure? (1
(b) Dukes A? (1)
(c) Dukes B and C? (1)
(d) Rectal tumours? (1)

Answer 11

Surgery:
- Laparoscopic surgery (resection)

• Endoscopic or local resection (Dukes A and cancer polyps)
• Adjuvant chemotherapy (Dukes B and C)
• Neoadjuvant radiotherapy (+/- chemotherapy) for rectal tumours prior to surgery

Question 12

Treatment: In colorectal cancer, what do operative treatments depend on? (3)

Answer 12

• Site of the tumour
• Size of the tumour
• Stage of the tumours

Question 13

Complications: What are the complications of colorectal surgery? (6)

Answer 13

Complications of colorectal surgery:

• Bleeding
• Anastomotic leak
• Infection (superficial and deep)
• Stoma problems (i.e ischaemia)
• Damage to pelvic nerves
• Possible impaired fecundity in younger women

Question 14

Extra: With respect to colon cancer, describe colorectal polyps (4)

Answer 14

Colorectal polyps: (ADENOMA)

• Protuberant growth (bulging)
• Epithelial
• Benign, pre-malignant
• Variety of histological types

Question 15

Extra: With respect to colon cancer, state 2 risks of colonoscopy? (2)

Answer 15

• Perforation

- Bleeding

Question 16

Extra: In the treatment of colon cancer, why may hepatectomy be performed?

Answer 16

• Liver metastasis

Question 17

Extra: In colon cancer, how do we determine the prognosis? (4)

Answer 17

For prognosis use:

• TNM staging
• Dukes’ staging
• Extramural venous invasion
• Resection