Colorectal Cancer Flashcards
Describe the adenoma- carcinoma sequence
Sequence of changes from normal mucosa to hyper- proliferative mucosa to adenoma and eventually to carcinoma
Incidence of adenomatous polyps and colorectal cancer in the general population
Polyps: 20 % in post mortem studies
Colorectal cancer: 5%
Which polyps are high risk
- Large polyps > 1 cm
- villous lesions
- sessile lesions
- high grade dysplasia
Most common region for polyps
Recto sigmoid colon
What parameters are used for the aetiology of colorectal cancer
- dietary parameters
- physical parameters
- inflammatory bowel disease
- familial risks
What diets are associated with increased risk of colorectal cancer
- high amounts of animal fat and meat
- substitution of fish and poultry is thought to reduce risk
- high intake of dietary fiber has been associated with a reduction in risk of colorectal cancer, maximum benefit is from wheat bran and cellulose
Physical parameters increasing the risk of colorectal cancer
- obesity –> increased insulin and insulin growth factor –> adenoma formation
- exercise is thought to be protective
Which are the hereditary cancers
- familial adenomatous polyposis
- attenuated FAP
- Lynch syndrome
- MUYTH associated polyposis
FAP is an autosomal dominant condition, where is the genetic defect
- chromosome 5 (APC gene)
When do patients with FAP manifest with disease
- manifest with polyps on teenage years
- Onset of cancer in fourth decade
What is Gardener’s syndrome (FAP)
Patients afflicted with colonic polyposis and extra intestinal manifestations
What is turcot’s syndrome
- polyposis in combination with brain tumor
When do patients with attenuated FAP present
- most patients present with polyps in the 4th to 5th decade
- cancer diagnosed after 6th decade
What is the lifetime risk of colorectal cancer in a patient with Lynch syndrome? What criteria are used to identify those at risk
- 80%
- Amsterdam criteria
Is MUYTH associated polyposis autosomal dominant or recessive
Recessive
What is the risk of colorectal cancer in a patient with IBD before and after 20 years duration of the condition
- less than 20: 5 %
- at 20 years: 10%
What are additional risk factors for colorectal cancer in patients with IBD
- greater extent of the disease
- evidence of mucosal dysplasia
- sclerosing cholangitis family history of cancer
- early onset IBD
If blood in the stool is found what is usually the next investigation
Colonoscopy
When should first degree relatives of cancer patients have a colonoscopy
10 years prior to the age of onset of disease in the affected relative
What percentage of colorectal cancers are recto sigmoid tumours
50-60%
Presentation of rectal tumour?
- bloody or mucoid discharge from the anus, alteration in bowel habit with/out tenesmus
- if presentation was delayed: features of obstructive symptoms and perianal pain
- discrete mass palpable on digital rectal exam
How do left sided colonic tumours present
- Intermittent constipation or diarrhea or both
- passage of blood per rectum may be reported
- weight loss
- delayed presentation: palpable mass or symptoms and signs of large bowel obstruction
How do right sided colonic tumours present
- unexplained anaemia and/or weight loss
- occult faecal blood
- advanced: abdominal mass
- non specific pain
What is the gold standard test for diagnosing colorectal carcinoma
Colonoscopy
