Colorectal Cancer Flashcards
Bowel cancer is the ____ most common in the UK
Bowel cancer is the ____ most common cause of cancer-related deaths in UK
- 4th most common (behind breast, prostate & lung)
- ** bowel cancer usually refers to cancer of colon or rectum as small bowel & anal cancers are less common*
- 2nd most common cause of cancer related deaths
Where is colorectal cancer common? (i.e. caecum, ascending colon, transverse colon etc…)
Location of cancer (averages)
- rectal: 40%
- sigmoid: 30%
- descending colon: 5%
- transverse colon: 10%
- ascending colon and caecum: 15%
What type of cancer are most colorectal cancers?
Adenocarcinoma
State some risk factors for colorectal cancer
- FH
- Familial adenomatous polyposis (FAP)
- Hereditary nonpolyposis colorectal cancer (HNPCC) (also known as Lynch syndrome)
- IBD
- Increased age
- Smoking
- Alcohol
- Diet (high in red & processed meat, low in fibre)
- Obesity
It is currently thought that there are 3 types of colon cancer (in terms of genetics); state these- highlighting how common each one is
- Sporadic (95%)
- Hereditary non-polyposis colorectal carcinoma (HNPCC, 5%)
- Familial adenomatous polyposis (FAP, <1%)
For familial adenomatous polyposis (FAP), discuss:
- Inheritance pattern
- Mutation
- What the mutation causes
- Relation to cancer
- Management
- Autosomal dominant
- Mutation in tumour suppressor gene, Adenomatous polyposis coli (APC) gene on chromosome 5
- Leads to hundreds of polyps (adenomas) in large bowel by age 30-40yrs
- Patients inevitably develop colorectal carcinoma. Also at risk of duodenal tumours.
- Generally have surgery (either partial colectomy, total colectomy with ileo-anal pouch formation or Panproctocolecotmy) in their 20’s
For hereditary non-polyposis colorectal carcinoma (HNPCC), discuss:
- Inheritance pattern
- Mutations
- Relation to cancers
- Criteria used to aid diagnosis
- Autosomal dominant
- At present 7 mutations identified, common genes involved MSH2 (60%), MLH1 (30%)
- 90% pts develop cancers which are usually poorly differentiated, highly aggressive & affecting proximal colon. Also at risk of other cancers (endometrial cancer is next most common)
- Amsterdam criteria
Discuss the bowel cancer screening programme in England, include:
- Who offered to & how often
- What test is used
- What happens if positive
- 60-74yrs (pts over 74yrs can request)
- Home FIT test every 2yrs
- If results positive sent for colonoscopy
For interest: at colonoscopy, approximately:
- 5 out of 10 patients will have a normal exam
- 4 out of 10 patients will be found to have polyps which may be removed due to their premalignant potential
- 1 out of 10 patients will be found to have cancer
How does a FIT test work?
What is advantage of FIT test over faecal occult test?
- Faecal immunochemical test is a type of faecal occult blood test which uses antibodies that specifically recognise human Hb; hence can detect and quantify amount of human blood in stool
- Advantages:
- Only detects human blood whereas conventional FOB tests would also detect animal blood (which had been ingested)
- Only 1 stool sample required whereas conventional FOB require 2-3
What are patients with risk factors for bowel cancer offered at regular intervals (to assess for bowel cancer)?
Colonoscopy at regular intervals
Example pts: IBD, HNPCC, FAP
State some signs & symptoms of colorectal cancer
How else may pts present? *HINT: it’s surgical emergency
- Change in bowel habit (usually to more loose and frequent stools)
- Unexplained weight loss
- Rectal bleeding
- Unexplained abdominal pain
- Iron deficiency anaemia (microcytic anaemia with low ferritin)
- Abdominal or rectal mass or ulceration on examination
- Abdominal pain
May also present as acute bowel obstruction (abdo pain, distension, constipation, nausea/vomiting)
Compare symptoms & signs of right-sided & left-sided colon cancer
Left Sided
- Fresh PR bleeding
- Early obstruction
- Early change in bowel habit
- Tenesmus
- Less advanced disease at presentation
Right Sided
- Occult bleeding, anaemia
- Late obstruction
- More advanced disease at presentation
Discuss the 2WW referral for colorectal cancer
Refer via 2WW if:
- >/= 40yrs with abdo pain and unexplained weight loss
- >/= 50yrs with unexplained rectal bleeding
- >/= 60yrs with a change in bowel habit or Fe deficiency anaemia
- Tested positive on FIT test
Consider urgent referral for people:
- Any age with a rectal or abdominal mass
- <50yrs with rectal bleeding and any of the following unexplained signs or symptoms:
- abdominal pain
- altered bowel habit
- weight loss
- iron deficiency anaemia
When might you use a FIT test in general practice?
To help assess for bowel cancer in pts who do not meet specific criteria for 2WW referral e.g.
- >/=50yrs with unexplained weight loss but no other symptoms
- <60yrs with change in bowel habit
… etc
What investigations are done for suspected bowel cancer?
- Colonoscopy with biopsy (GOLD STANDARD)
- Staging CT/CT TAP
- Rectal MRI: if tumour is below peritoneal reflection
- Blood tests:
- FBC: may see anaemia
- Fe studies: may see low ferritin
- LFTs: baseline liver
- U&Es: baseline renal
- CEA: tumour marker
Other imaging investigations may include flexible sigmoidoscopy (limitations as only visualise part of bowel), CT colonography (if not suitable for colonoscopy)
What classification was previously used for bowel cancer? (Now been replace by TNM classification)
Dukes’ Classification
Dukes’ classification is the system previously used for bowel cancer. It has now been replaced in clinical practice by the TNM classification, but you may come across it in older textbooks or question banks. A brief summary is:
- Dukes A – confined to mucosa and or growing slightly into muscularis propria
- Dukes B – extending through the muscle of the bowel wall
- Dukes C – lymph node involvement
- Dukes D – metastatic disease
Resections, for colorectal cancer, are tailored around what?
The lymphatic drainage of the colon follows the arterial supply and therefore most resections are tailored around the resection of particular lymphatic chains (e.g. ileo-colic pedicle for right sided tumours).
Lots of different surgeries may be performed for colorectal cancer; describe each of the following:
- Right hemicolectomy
- Left hemicolectomy
- Anterior resection (sometimes known as high anterior resection)
- Low anterior resection
- Ultra-low anterior resection
- Abdomino-perineal resection
- Hartmann’s procedure
- Right hemicolectomy: caecum, ascending & proximal transverse colon
- Left hemicolectomy: distal transverse & descending colon
- Anterior resection (high anterior resection): sigmoid colon
- Low anterior resection: sigmoid & upper rectum
- Ultra low anterior resection: sigmoid & lower rectum
- Abdomino-perineal resection: rectum & anal sphincters (+/- sigmoid colon)- permanent colostomy. Involvement of sphincter complex or very low tumour needs APR.
- Hartmann’s procedure: sigmoid resection with end colostomy
