[2] Colorectal Cancer Flashcards
How does the incidence of colorectal cancer differ from other cancers?
It is the third most common cancer in the UK
How does the mortality of colorectal cancer differ from other cancers?
It has the second highest mortality figures of any cancer
What is the occurrence of colorectal cancer strongly associated with?
Age
What % of presentations of colorectal cancers are in patients in those >60 years?
85%
Can colorectal cancers occur in patients 20-30 years of age?
Yes, particularly in inherited cancer syndromes
Where do colorectal cancers originate from?
The epithelial cells lining the colon or rectum
What is the most common type of colorectal carcinoma?
Adenocarcinomas
What are the rarer types of colorectal carcinoma?
Lymphoma
Carcinoid
Sarcoma
How do most colorectal cancers develop?
Via a progression of normal mucosa to colonic adenoma (colorectal polyps), to invasive adenocarcinoma
How long can adenomas be present before becoming malignant?
10 years or more
What % of adenomas progress to adenocarcinomas?
10%
What genetic mutations have been implicated in predisposing individuals to colorectal cancer?
Adenomatous polyposis coli (APC) gene
Hereditary non-polyposis colorectal cancer (HNPCC)
What is the APC gene?
A tumour suppressor gene
What does early APC gene mutation and inactivation result in?
Growth of adenomatous tissue
What condition is APC mutation responsible for the development of?
Familial adenomatous polyposis (FAP)
What happens in HNPCC?
Mutation to DNA mismatch repair genes lead to defects in DNA repair
What does HNPCC commonly account for?
The familial risk associated with colorectal cancer
What % of colorectal cancers are sporadic?
Approximately 75%
What is meant by sporadic in colorectal cancer?
Developing in people with no specific risk factors
What are the risk factors for colorectal cancer?
Age >60 years Family history Inflammatory bowel disease Low fibre diet High processed meat intake High alcohol intake Smoking
What are the common clinical features of bowel cancer?
5
Change in bowel habit Rectal bleeding Weight loss Abdominal pain Iron-deficiency anaemia
When is progressive weight loss present in colorectal cancer?
Only with associated metastasis, or rarely sub-acute bowel osbtruction
What symptoms may be present with a right-sided colon cancer?
Abdominal pain
Occult bleeding
Mass in right iliac fossa
What symptoms may be present with a left-sided colon cancer?
Rectal bleeding
Change in bowel habit or tenesmus
Mass in left iliac fossa/mass on PR exam
When should patients be referred for urgent investigations for suspected bowel cancer?
40 or older with unexplained weight loss and abdominal pain
50 or older with unexplained rectal bleeding
60 or older with iron-deficiency anaemia or changes in bowel habit
Positive occult faecal blood test
What are the differential diagnoses for colorectal cancer?
Inflammatory bowel disease
Haemorrhoids
Diverticulitis
How can inflammatory bowel disease be differentiated from colorectal cancer?
The average age of onset is younger (20-40years)
Typically presents with diarrhoea containing blood and mucus
How is haemorrhoids differentiated from colorectal cancer?
Bright red rectal bleeding covering the surface of the stool
Rarely presents with abdominal discomfort or pain, altered bowel habits, or weight loss
How can diverticulitis be differentiated from colorectal cancer?
It is likely to cause systemic features of inflammation
What is the UK screening programme for colorectal cancer?
In the UK, screening is offered every 2 years to men and women aged 60-75 years using faecal occult blood home testing kits
How many samples are required for analysis with faecal occult blood home testing kits?
3 separate stool samples
What happens if any of the stool samples in screening are positive?
The patient is offered an appointment with a specialist nurse, and further investigation is conducted with colonoscopy
How effective is the colorectal cancer screening programme at detecting cancer?
Since its induction, it has increased the detection of colorectal cancer in people aged 60-69 by 11%
What investigations might be done in suspected colorectal cancer?
Routine bloods
Coloscopy with biopsy
Other imaging
What blood tests should be performed for suspected colorectal cancer?
FBC
U&Es
LFTs
Coagulation screens
What might FBC show in colorectal cancer?
May be microcytic anaemia, especially if cancer is on right side of colon
What is the use of CEA in colorectal cancer?
It should not be used as a diagnostic test, but can be used to monitor disease progression
When should CEA be performed in other to screen for recurrence?
Pre- and post-treatment
Why should CEA not be used for diagnosis of colorectal cancer?
Due to poor sensitivity and specificity
What is the gold standard for diagnosis of colorectal cancer?
Colonoscopy with biopsy
What can be used if coloscopy is not suitable for the patient?
CT colography or flexible sigmoidoscopy
Why may a patient not be suitable for colonoscopy?
Frailty
Co-morbidities
Intolerance
What is the disadvantage of CT colography or flexible sigmoidoscopy compared to colonoscopy?
It is not as sensitive or specific as colonoscopy