[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
What other imaging investigations are required once the diagnosis is made?
CT chest/abdo/pelvis
MRI rectum
Endo-anal ultrasound
What is the purpose of the CT chest/abdo/pelvis in colorectal cancer?
Look for distant metastasis and local invasion
How can full colonoscopy or CT colonogram be used in confirmed diagnoses of colorectal cancer?
To check for a 2nd tumour, if not used initially
When is a MRI rectum required in confirmed cases of colorectal cancer?
Rectal cancers only
What is the purpose of MRI rectum in colorectal cancers?
To assess the depth of invasion, and hence the need for pre-operative chemotherapy
When is an endo-anal ultrasound required in confirmed colorectal cancer?
Early-rectal cancers (T1 or T2) only
What is the purpose of an endo-anal ultrasound in early rectal cancers?
To assess suitability for trans-anal resection
How can colorectal cancers be staged?
TNM
Dukes staging
What does TNM staging stage cancers depending on in colorectal cancer?
The depth the tumour invades the bowel wall
The extent of spread to local lymph nodes
If distant mets are present
Is the Duke’s staging system used?
It has been largely superseded, but is still used at some centres for additional staging detail
What constitutes a Dukes A?
Confined beneath the muscularis mucosa
What is the 5 year survival of Dukes A cancer?
90%
What constitutes a Dukes B?
Extension through the muscularis mucosa
What is the 5 year survival of Dukes B cancer?
65%
What constitutes a Dukes C?
Involvement of regional lymph nodes
What is the 5 year survival of Dukes C cancer?
30%
What constitutes a Dukes D?
Distant metastasis
What is the 5 year survival of a Dukes D cancer?
<10%
What are the treatment options for colorectal cancer?
The only definitive curative treatment is surgery, yet chemotherapy and radiotherapy have an important role as neoadjuvant/adjuvant treatment, as well as pallitation
Where is surgery the mainstay of curative management of colorectal cancer?
For localised malignancy in the bowel
What is the general plan in most surgical management for colorectal cancer?
Suitable regional colectomy followed by primary anastomosis or formation of a stoma
What is the purpose of a regional colectomy in colorectal cancer?
To ensure removal of the primary tumour with adequate margins and lymphatic drainage,
What is the purpose of primary anastomosis or formation of a stoma in colorectal cancer?
To restore bowel function
What are the types of regional colectomy?
Right hemicolectomy and extended right hemicolectomy Left hemicolectomy Sigmoidcolectomy Anterior resection Abdominoperineal resection
Where is a right hemicolectomy used?
For caecal or ascending colon tumours
What happens to the vessels during a right hemicolectomy?
The ileocolic, right colic, and right branch of the middle colic vessels are divided and removed with their mesenteries
What is an extended right hemicolectomy typically performed for?
Any transverse colon cancers
Where is a left hemicolectomy used?
For descending colon cancers
What happens to the vessels during a left hemicolectomy?
The left branch of the middle colic vessels, the inferior mesenteric vein, and the left colic vessels are divided and removed with their mesenteries
Where is a sigmoidcolectomy used?
For sigmoid colon tumours
What happens to the vessels during a sigmoidcolectoym?
The IMA is fully dissected out with the tumour to ensure adequate margins are obtained
Where is an anterior resection used?
For high rectal tumours, typically if >5cm from anus
Why is an anterior resection approach favouring in rectal carcinoma?
As resection leaves the rectal sphincter in tact and functioning if anastomosis is performed, unlike AP resections
What is often performed with anterior resections?
A defunctioning loop ileostomy
Why is a defunctioning loop ileostomy often performed with anterior resections?
To protect the anastomosis, and reduce complications in the event of an anastomotic leak
What happens to a defuntioning loop ileostomy long term?
It is reversed electively approx. 4-6 months later
Where is an abdominoperineal resection performed?
Low rectal tumours, typically <5cm from anus
What does an abdominoperineal resection involve?
Excision of the distal colon, rectum, and anal sphincters
What does an abdominoperineal resection result in long-term?
A pernament colostomy
Why are bowel resections often performed laparoscopically?
As this offers faster recovery times, reduced surgical site infection risk, and reduced post-operative pain, with no difference in disease recurrence or overall survival rates when compared to open surgery
Where is a Hartmann’s procedure used?
In emergency bowel surgery, such as bowel obstruction or perforation
What does a Hartmann’s procedure involve?
A complete resection of the recto-sigmoid colon with the formation of an end-colostomy and the closure of the rectal stump
Where is chemotherapy typically indicated in colorectal carcinoma?
In patients with metastatic disease
How the decision on what chemotherapy agents to use made in colorectal cancer?
Will be decided by MDT
Give an example of a chemotherapy regime used for patients with metastatic colorectal cancer?
FOLFOX - folinic acid, fluorouracil, and oxaliplatin
What kind of colorectal cancer can radiotherapy be used in?
Rectal cancer
What is the role of radiotherapy in rectal cancer?
Most often as a neo-adjuvant treatment
Why is radiotherapy rarely given in colon cancer?
Due to the risk of damage to the small bowel
Where is radiotherapy of particular use?
In patients with rectal cancers which look in MRI to have a ‘threatened’ circumferential resection (i.e. within 1mm)
What can be done in patients with rectal cancers with a ‘threatened’ circumferential resection?
They can undergo a pre-operative long-course chemo-radiotherapy to shrink the tumour, thereby increasing the chance of complete resection and cure
How will many high staging colorectal cancers be managed?
Palliatively
What is the purpose of the palliative management of colorectal cancer?
Reducing cancer growth and ensuring adequate symptom control
What are the important surgical options for palliative care available?
Endoluminal stenting
Stoma formation
Resection of secondaries
What is the purpose of endoluminal stenting in colorectal cancer?
It can be used to relieve acute large bowel obstruction in patients with left sided tumours
Why can endoluminal stenting not be used in low rectal tumours?
Due to the unpleasant side-effects of intractable tenesmus
What are the main side-effects of endo-luminal stenting?
Perforation
Migration
Incontinence
What is the purpose of stoma formation in colorectal cancer?
Relieve acute obstruction
How is stoma formation usually performed to relieve acute obstruction in colorectal cancer?
Either a defunctioning stoma or pallative bypass
When can resection of metastases be done?
With adjuvant chemotherapy for any liver mets
When should patients receiving curative treatment for colorectal cancer first be followed up?
4-6 weeks after finishing treatment
How many CT CAP’s should a patient receive in the first 3 years after curative treatment for colorectal cancer?
At least 2
What should patient be offered 1 year after surgery for colorectal cancer?
Colonoscopy
If the colonoscopy is normal after surgery for colorectal cancer, when should the patient have another?
5 years
When should follow-up following treatment for colorectal cancer be stepped down?
When patient and clinician agree risk of further testing outweighs the benefits
What should patients who have suspected return of colorectal cancer be offered?
Same level of testing as they had the first time
