colorectal cancer Flashcards
What are colorectal cancers?
Most colorectal cancers are adenocarcinomas that evolve from polyps, which may be present for ten years or more before malignancy develops. Colorectal cancer is locally invasive but metastatic spread may be evident before local growth produces symptoms. The most common site for metastatic spread is the liver. Other sites (eg, the lungs, brain and bone) are unusual in the absence of liver metastases.
What age group experiences the most colorectal cancers?
85-89
What is the most common site for colorectal cancer?
Rectum
What are the risk factors for colorectal cancers?
- Family history
- Inflammatory bowel disease
- Polyposis syndromes
- Diet rich in meat, low in fibre
- Alcohol, obesity, smoking
What family history puts you at risk of developing colorectal cancer?
Lynch syndrome
Gardner syndrome
Familial adenomatous polyposis
What cells does colorectal cancer originate from?
Epithelial cells
What is the pathogenesis of colorectal cancer?
Mutation in Wnt signalling pathway inntestinal crypt stem cells
Mutation in APC and KRAS genes
P53 mutation
At what age does colorectal cancer screening start?
60, this is realistically too late
What is the adenoma-carcinoma sequence?
Normal → hyperproliferation → micro-adenoma → small/intermediate/large adenomous polyp → cancer
Takes 10-15 years to develop
What are the mutation in Lynch that are associated with colorectal cancer?
MLH1
MSH2
MSH6
PMS2
Makes for absence of mismatch repair system in nucleus
What is a key characteristic in Lynch syndrome?
DNA mismatch repair which causes microsatellite instability
Used as a screening tool for mismatch repair defects in DNA
How is Lynch syndrome inherited?
Autosomal dominant
What are the Amsterdam criteria in Lynch syndrome?
3-2-1 rule for diagnosing Lynch
3 relatives with bowel cancer in 2 generations, 1 is a first degree relative and 1 had cancer by the age of 50
What is the clinical history of Lynch syndrome?
- Family history
- Onset < 45 years
- Proximal cancers
- Multiple synchronous primary cancers
- Mucinous, poorly differentiated lymphocyte infiltration and singlet ring formation
What are symptoms of right colon cancers?
Weight loss, silent colon, anaemia, occult bleeding, mass in right iliac fossa, disease more likely to be advanced at presentation
What are symptoms of left colon cancers?
Colicky pain, rectal bleeding, bowel obstruction, tenesmus, mass in left iliac fossa, early change in bowel habit, less advanced disease at presentation.
What are the most common presenting complaints for colorectal cancer?
Rectal bleeding
Persistent change in bowel habit
Anaemia
In colorectal cancer, what do jaundice and hepatomegaly present?
Advanced disease and liver metastases
When would you do faecal immunochemical testing?
Adults without rectal bleeding who:
- Are aged 50 or over with unexplained abdominal pain or weight loss; or
- Are aged under 60 with changes in their bowel habit or with iron-deficiency anaemia; or
- Are aged 60 and over and have anaemia even in the absence of iron deficiency.
What investigations would you do for suspected colorectal cancer?
- FBC + LFT (anaemia, alkaline phosphatase raised in liver metastases)
- Colonoscopy with biopsy
- eGFR to know whether you can use contrast
- CT scan
When would you refer someone for suspected colorectal cancer?
- Aged 40 years and over with unexplained weight loss and abdominal pain; or
- Aged 50 and over with unexplained rectal bleeding; or
- Aged 60 and over with anaemia or changes in bowel habit
What would you use to stage colorectal cancer?
Contrast-enhanced CT and Dukes’ staging classification
What are the stages of Dukes’ staging classification?
Dukes’ A - the cancer is only in the innermost lining of the bowel or slightly growing into the muscle layer.
Dukes’ B - the cancer has grown through the muscle layer of the bowel.
Dukes’ C - the cancer has spread to at least one lymph node close to the bowel.
Dukes’ D - the cancer has metastasised to other areas - eg, the liver, lungs or bones.
How would you manage colorectal cancer?
Surgery
1. Right hemicolectomy: for tumours in the caecum, ascending and proximal transverse colon.
2. Left hemicolectomy: if in the distal transverse colon or descending colon.
3. Sigmoid colectomy: for tumours of the sigmoid colon.
Anterior resection: if in the low sigmoid or high rectum. Anastomosis is achieved at the first operation.
Radiofrequency ablation for liver metastases
