Bowel Cancer Flashcards
What is the most common form of bowel cancer?
Adenocarcinoma (gland forming)
Others:
lymphomas
Sarcomas
Can cancer occur in small bowel?
Less common but yes
Why is bowel cancer so dam important?
Common
Curable if detected early
Significant morbidity due to bowel
Is bowel cancer more likely in men or women?
Men, more likely to die as well
What are chances of getting bowel cancer?
1/46
Second most common cause of death in men and women
What are risk factors for bowel cancer?
1) Family history - increases risk by 1.5x
- 3x if multiple
- 5x if under age 45
2) Inflammatory bowel disease
3) Obesity
4) Diet
Why has 5 year survival increased so much?
Early detection
Identification of high risk individuals
New drugs
What are the complications or symptoms of colon cancer?
Early = blood in stool (melaena)
Advanced =
System effects
- bowel obstruction, perforation
Systemic effects
- Metastatic spread to other organs
- Cachexia
- Paraneoplastic symptoms
- Death
What are the four classes of regulatory genes?
Growth promoting oncogenes (gain function)
Growth inhibiting tumour supressors (loss of function)
Genes that regulate cell death (pro-apoptotic)
Genes involved in DNA repair
What are the stages to colon cancer?
Normal mucosa Mucosa at risk Adenoma - polyp Advanced adenoma - large irregular polyps Carcinoma - invade bowel wall
What are the 3 main pathways to colon cancer?
Chromosomal Instability
Microsatellite Instability (MRE deficiency)
CpG island Methylation
What is APC?
A tumour supressor gene, downregulates E cadherin and B-cantenin, Wnt siglanning
What is B-cantenin?
Proto-oncogene, upregulates multiple growth pathways
What are the steps to carcinoma?
APC at 5q21 = mucosa at risk
APC B-cadherin = adenoma
KRAS at 12p12 = advanced adenoma
p53 = carcinoma
What are the two main types of familial colon cancer?
Familial Adenomatous Polyposis (FAP)
HNPCC (Lynch syndrome)
What is FAP?
Familial Adenomatous Polyposis
- auto dominant 1 in 30 000
- 100% risk of CC
- Mutation in APC at 5q21
- Carpet of adenomas
- Prophylactic total colectomy by age 25
What is HNPCC?
Hereditary nonpolyposis colorectal cancer
- Auto dominant 1 in 600 - 2000
- Fewer polyps
- Mutations in MRE genes
- Inherited Microsatelite instability
- Risk of bowel, endometrial, bladder, gastric + skin
How does colon cancer usually form though?
Sporadic
How is colon cancer diagnosed?
Personal history and family history
Clinical symptoms
- Altered blood
- Pain/weight loss/ bowel obstruction only when advanced
Clinical signs = usually none
- Palpable mass (advanced)
Radiological findings
- May be none
- Mass or obstruction (advanced)
Endoscopic findings
Pathologic Findings
- Macroscopic
- Microscopic
- Immunohistochemical
- Molecular genetic
What is the national bowel cancer screening program and what do they look for?
Faecal occult blodd (not visible)
Reducing mortality rate by 30%
Immunochemical test for globin - 2 samples - Uses new hemtube assay - Offered 5 yearly to > 50 year olds Being expanded to 2 yearly?
What happens in national bowel cancer screening detect faecal occult blood?
Refer for colonoscopy
If polyp found removed via endocsopic resection
Large mass biopsied
What does like screening even mean?
Screening means testing asymptomatic people for disease or precurser
What are the advantages of bowel cancer screening?
Reduction in mortality and morbidity
Cost effective
Procedures for early cancer easier and safer
What are the disadvnatages for bowel cancer screening?
Costly
Risk of additional intervention
