Colorectal Cancer

Question 1

What are the risk factors for colorectal carcinoma?

Answer 1

• adenomas (size, number, villous)
• history of IBD (esp UC due to longstanding inflammatory episodes)
• increasing age
• obesity + sedentary lifestyle
• high fat, low fibre diet
• smoking + alcohol
• family history of polyps (FAP - associated with APC)

Question 2

What are the 3 main routes for the molecular pathogenesis of colorectal cancer?

Answer 2

• adenoma-carcinoma sequence: stepwise pattern of mutation activation of oncogenes and inactivation of tumour suppressor genes that lead to cancer (majority of cases)
• microsatellite instability: dysfunction in DNA mis-match repair genes resulting in genetic hyper-mutability
• abhorrent hypermethylation: epigenetic modification where methylation in genes causes mutation in function

Question 3

What features of adenomas increase the risk of the development of cancer?

Answer 3

• high grade
• villous
• tumour size >10mm
• increasing number of polyps

Question 4

Describe the TNM 8 staging of colorectal cancer

Answer 4

• T1: invasion into submucosa
• T2: invasion into, but not through muscularis propria
• T3: invasion through muscularis propria, into sub serosa or non-peritonealised pericolic/perirectal tissue
• T4: invasion of visceral peritoneum (a) and/or other organs (b)
• N0: no regional lymph node mets
• N1: 1-3
• N2: 4+
• M0: no distant mets
• M1: distant mets

Question 5

Describe the staging of colorectal cancer

Answer 5

• stage 1: T1/2, N0, M0
• stage 2: T3/4 N0 M0
• stage 3: T any, N1/2 M0
• stage 4: T any N1/2 M1