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
What is the definition of an adenoma?
How are colonic adenomas classified?
a benign neoplasm of glandular epithelium
they are classified by:
architecture:
- this is whether they are tubular, villous or tubulovillous
degree of dysplasia:
- this is either low-grade or high-grade
Why are polyps clincally significant?
they can be precursors to colorectal cancer
What 3 factors increase the risk of malignant transformation of a polyp?
size:
- > 1cm means high risk
histological architecture:
- villous adenomas have a high risk
severity of dysplasia:
- high-grade dysplasia links with high risk
What is the first location that bowel cancer often metastasizes to and why?
once cancer cells access the venous system in the bowel, they metastasize to the liver
blood from the bowel is drained to the liver
What is the current NHS bowel cancer screening programme in the UK?
screening every 2 years for men and women aged 60-74
(this is being lowered to 50)
this is performed by faecal immunochemical test (FIT) to observe hidden blood in the stool
any positive tests are invited for colonoscopy
What is the benefit to the NHS bowel cancer screening programme?
cancers can be picked up before they are symptomatic
this means they can be treated before there is a risk of the cancer spreading
What are the main risks associated with colonoscopy?
1 in 1,500 chance of bowel perforation
1 in 10,000 risk of death
What are the most common locations for bowel cancers to develop?
the sigmoid colon and the rectum
these can be accessed by slightly less invasive procedures
What is meant by an adenocarcinoma?
a malignant gland-forming tumour of epithelial origin
Typically, what actually is the definition of colorectal cancer?
cancer affecting the terminal part of the gut
What are the treatment options available for colorectal cancer?
surgical resection +/- other preoperative therapies
- right hemicolectomy
- left hemicolectomy
- anterior resection
- transverse colectomy
When may CT scans be used in colorectal cancer patients?
CT scans are important in staging
this involves ensuring that the tumour has not spread elsewhere
What are the following parts of the large bowel?
In a hemicolectomy, what other structures are removed?
the associated lymph nodes and venous drainage
What is meant by “staging” of colorectal cancer?
What are the 2 types of staging and why is it important?
it is the determination of the extent of spread of a tumour at presentation
There is TNM and Duke’s staging
It determines treatment and prognosis
What is involved in TNM staging?
TUMOUR NODES METASTASIS
- T shows how far through the bowel wall the cancer has spread
- N shows the number of lymph nodes the cancer has spread to
- M represents distant metastases
How does staging influence treatment options?
staging determines whether patients are given additional chemotherapy
stage 3 or 4 cases are given chemotherapy to improve chances of survival
What type of blood test is usually used as a follow-up treatment for colorectal cancer patients?
CEA (carcinoembryonic antigen) blood test
it is used to help diagnose and manage certain types of cancers
using this blood test can show whether a particular cancer treatment is working
What is Hartmann’s procedure and why is it used in colorectal cancer?
it is also known as a proctosigmoidectomy
surgical resection of the rectosigmoid colon with closure of the anorectal stump and formation of an end colostomy
What are metastases?
metastasis is when cancer spreads to a different body part from where it started
metastases is the pleural of metastasis
What routes do tumours metastasize by?
cancer cells break away from the main tumour and enter the blood or lymphatic system
cancer cells may also break off of the primary tumour and grow in a nearby area
