Colorectal cancer

Question 1

Epidemiology colorectal cancer?

Answer 1

3rd most common cancer in developed world

Question 2

What type are majority of colorectal cancers?

Answer 2

Adenocarcinomas (cancer that forms in glandular tissue) derived from epithelial cells

Question 3

Proportion of colorectal cancers in colon (proximal and distal) vs rectum respectively?

Answer 3

66% colon
33% rectum

Question 4

Less common types of malignant colorectal cancers? (3)

Answer 4

Carcinoid tumours, gastrointestinal stromal cell tumours, lymphomas

Question 5

General pathophysiology of colorectal cancers?

Answer 5

Majority arise from adenomatous polyps→ invasive colorectal cancer

Multi-step process: inactivation of tumour-suppressor and DNA repair genes, w simultaneous activation of oncogenes

Question 6

Key tumour suppressor gene involv in colorectal cancer?

Answer 6

Adenomatous polyposis coli (APC) tumour suppressor gene

Question 7

Pathophysiology of metastases of colorectal cancer?

Answer 7

Spread via local lymph nodes, enteric venous drainage to liver, and haematogenously to lungs (and less commonly to bone and brain)

Question 8

Aetiology and risk factors of colorectal cancer?

Answer 8

Increasing age

Genetic and environmental factors

Family Hx and family cancer syndromes (ie: familial adenomatous polyposis (FAP), Lynch syndrome)
Environmental modifiable risk factors: obesity, low fibre diet, smoking, alcohol, low VitD

Question 9

Staging of colorectal cancer: T?

Answer 9

Tis: in situ. Only in mucosa
T1: only in inner layer- submucosa
T2: in muscle layer- muscularis propria
T3: grown into outer lining BUT not through it- subserosa
T4a: grown through outer lining and into visceral periotneum
T4b: grown through wall and into/ attached to nearby organs

Question 10

Staging of colorectal cancer: N?

Answer 10

N0: no lymph node involvement
N1: 1-3 lymph nodes
N2: 4-7+

Question 11

Staging of colorectal cancer: M?

Answer 11

M0: not spread to other organs
M1: spread to other organs (and peritoneum)

Question 12

Risk factors for colorectal cancer?

Answer 12

• Increased age
• Family Hx
• Adenomatous polyposis coli mutation
• Lynch syndrome (hereditary non-polyposis colorectal cancer)
• IBD
• Obesity

Question 13

Signs and symptoms of colorectal cancer? (for L and R see notes)

Answer 13

• Rectal bleeding
• Change in bowel habit
• Rectal/ abdo mass
• Anaemia
• Abdominal pain and distention
• Weight loss and anaemia
• Palpable lymph nodes
• May present w ascites/hepatomegaly/bone pain

Question 14

Investigations for colorectal cancer?

Answer 14

FBC, LFTs, renal function
MUST have DRE if present w anal bleed

Colonoscopy
CTAP
Genetic testing

Consider: MRI pelvis, biospy, PET

Question 15

Management of colorectal cancer?

Answer 15

Surgical resection main curatative treatment for localised colorectal cancer

Suitable for surgery: surgical resection w/ wo pre+/postop chemoradiotherapy

NOT suitable for surgery: chemotherapy

Question 16

Factors to consider when deciding whether or not to surgically resect colorectal cancer?

Answer 16

• Risks, age, comorb
• Diameter and location
• Margins of tumour
• Histology
• Lymphovascular invasion

Question 17

What is Lynch syndrome?

Answer 17

Also known as hereditary non-polyposis colorectal cancer (HNPCC)- most common cause of hereditary colorectal cancer

Autosomal dominant
Mismatched repair genes that don’t work as expected→ if error happens in DNA, may not get fixed→ could cause cells to grow out of control and become cancerous