Colorectal Cancer Flashcards
What are the 3 red flag symptoms for bowel cancer?
- rectal bleeding
- weight loss
- family history
What is significant to ask if there is a family history of colorectal cancer?
the age of the family members when they were affected
this is more concerning if they were younger
If a GP suspects potential colorectal cancer, who do they refer to?
What does this person do when they meet the patient for the first time?
they refer for a secondary care opinion to a colorectal surgeon
the surgeon takes a full clinical history and performs a full clinical examination, including a digital rectal examination
What are the 3 main risk factors for colorectal cancer?
- increased age
- male gender
- family history
What are the other 6 risk factors for colorectal cancer?
- obesity and sedentary lifestyle
- smoking and drinking alcohol
- eating too much red meat
- eating too little fruit/vegetables
- idiopathic inflammatory bowel disease
- previous polyps/cancers in the bowel
How can the risk of colorectal cancer be reduced?
- increasing fibre intake
- having a healthy diet including fruit and vegetables
- aspirin reduces the risk of developing polyps
What are the 2 types of colorectal cancer?
sporadic CRC - accounts for 90-95% of cases
hereditary CRC - accounts for 5-10% of cases
What may suggest that someone has sporadic colorectal cancer?
there is no evidence of a hereditary syndrome
there may still be a familial component
What are the 2 main hereditary syndromes responsible for causing hereditary colorectal cancer?
- familial adenomatous polyposis (FAP)
- Lynch syndrome
What type of inheritance is seen in FAP?
What gene is affected?
autosomal dominant inheritance
the affected gene is the adenomatous polyposis coli (APC) gene
When do tumours tend to develop in FAP?
Are these cancerous?
tumours develop very early (2nd decade)
the bowel becomes covered with a minimum of 100 polyps
carcinoma occurs inevitable by 40 years
What is the major preventative treatment in FAP?
prophylactic colectomy is performed in late teens/early 20s
this involves removal of the entire large bowel
What is the Vogelstein sequence?
the idea that cancer is caused by sequential mutations of specific oncogenes and tumor suppressor genes
How is the mutation in the APC gene in FAP related to the Vogelstein sequence?
it is the first mutation in the sequence
having the APC mutation means the patient’s bowel is in a primed state for hyperproliferation
What is significant about the number of polyps in the bowel of someone with FAP?
the risk of any one adenoma (polyp) undergoing malignant transformation is 5%
the excessive number of polyps greatly elevates the combined risk
What type of inheritance is seen in Lynch syndrome?
What mutation is involved?
autosomal dominant inheritance
it is caused by a mutation in one of the six DNA mismatch repair genes that are part of the microsatellite instability pathway
What is the role of a mismatch repair gene?
they code for proteins that repair any damage to the genome
How is Lynch syndrome related to the Vogelstein sequence?
IT ISNT
Mutations in DNA mismatch repair genes follow an alternative pathway for CRC development outside of the Vogelstein sequence
this accounts for around 15% of cases
Why is a colonoscopy the “gold standard” test when further investigating a patient?
biopsies can be taken during the procedure to make a tissue diagnosis
this cannot be done on imaging
What is a CT colonography?
a colonoscopy is recreated virtually
this is less invasive than a colonoscopy which is significant if there are comorbidities present
if something is identified on the scan, biopsies then need to be taken
If a polyp is identified on a colonoscopy, what is done to it?
the polyps are removed by polypectomy
this is because there is a chance that they may develop into a cancer
What type of polypectomy is used for a pedunculated polyp?
this is a polyp that hangs from the colon wall on a stalk of bowel tissue
it is removed by snare polypectomy
What type of polypectomy is used for sessile polyps?
these are flat polyps that are directly attached to the bowel wall
they are removed by endoscopic mucosal resection
What is the definition of a polyp?
What are the 2 different categories of polyps found in the bowel?
a polyp is a tissue mass that protrudes into the bowel lumen
hyperplastic & inflammatory polyps:
- these do not have a chance of turning into a cancer
adenomatous polyps:
- there is a 5% chance that these could turn into cancer
