Colorectal Cancer Flashcards
Explain the epidemiology of colorectal cancer
Second largest cause of cancer death
3rd commonest cancer diagnosis
2 thirds colic and 1 third rectal
Describe colorectal cancer and genetics
Most are sporadic - no familial genetic influence
10% have familial risk
HPNCC, FAP, MAP
What are the risk factors for sporadic cases of colorectal cancer?
Age, male gender, previous adenoma/ CRC and environmental influences - diet, obesity, lack of exercise, smoking and diabetes
Describe colorectal polyps
Protuberant growths and variety of histological types
Can be benign or malignant
Epithelial or mesenchymal
What are adenomas?
Benign and pre-malignant
Epithelial in origin
Can be tubular, villous or tubulo-villous
Pedunculated or sessile
What promotes cell growth, proliferation and apoptosis?
Activation of oncogene
Loss of tumour suppressor gene
Defective DNA repair pathway genes
What is the presentation of colorectal cancer?
Rectal bleeding, altered bowel opening to loose stools, iron deficiency, rectal or lower abdomen mass, acute chronic obstruction
Systemic symptoms of malignancy
Describe colonoscopy for investigation of colorectal cancer
Investigation of choice
Allows tissue biopsy
Therapeutic as well as diagnostic - polypectomy
What are some problems with a colonoscopy?
Sedation
Bowel preparation
Risks are perforation and bleeding
What radiological imaging is used for colorectal cancer?
Barium enema
CT colonography - 3d virtual colonoscopy
CT abdo pelvis
What are some problems with radiological imaging of colorectal cancer?
Ionising radiation
Bowel prep
No histology
No therapeutic intervention
What are some staging investigations used?
CT scan chest/abdomen/pelvis
MRI
PET scan
What staging is used for colorectal cancer?
Duke’s staging
A-D
Describe surgery in colorectal cancer
80% need surgery
Dukes A - endoscopic or local resection
Depends on site and shape
May need laparotomy, laparoscopic, stoma formation, removal of lymph nodes
When is chemo used for colorectal cancer?
Adjuvant
Dukes C and maybe B
Positive lymph node histology
Mops up micro metastases
Agents - 5-FU
When is radiotherapy needed for colorectal cancer?
Rectal cancer only
Is neoadjuvant and can also can involve chemo to control tumour before surgery
What is involved in palliative care for colorectal cancer?
Chemo, colonic stenting to prevent obstruction
Describe duke’s staging and prognosis
5 year survival decreases from A to D from 83% to 3%
What is the aim of population screening?
Detect pre-malignant adenomas and early cancers in general population
What are the modalities for population screening of colorectal cancer?
Faecal occult blood test (FOBT)
Faecal immunochemical test (FIT)
Flexible sigmoidoscopy
Colonoscopy
CT colonography
What is the Scottish bowel screening programme?
Roll out in 2007
50-74 years
FOBT every 2 years and if positive then colonoscopy
but has lower positivity in women and high interval cancer rate
What is the FIT in Scotland?
Faecal immunochemical testing
Specific for human haemoglobin
Automated and quantitative
What are heritable conditions for colorectal cancer?
FAP, MAP, HNPCC
What groups are screened for colorectal cancer?
Heritable conditions
Inflammatory bowel disease
Familial risk
Previous adenomas/CRC
Explain FAP
Autosomal dominant condition
Can show young
Mutation of the APC gene on chromosome 5
Annual colonoscopy from age 10-12
Prophylactic proctocolectomy age 16-25
What are some manifestations of FAP?
Extracolonic -Benign gastric fundic cystic hyperplastic
Duodenal adenomas
Desmoid tumours
CHRPE
What is NSAIDs chemoprevention of FAP?
Sulindac reduces polyp numbers and prevents recurrence of higher grade adenomas
Explain MAP
Autosomal recessive
Caused by pathogenic variants in the MUTYH base excision repair gene
CRC is most likely to be right sided and synchronous
When is surveillance in MAP?
Annual age starts at 18-20
Duodenal adenomas so GI surveillance at 35years
Explain HNPCC
Autosomal dominant condition
Mutation in DNA repair genes
Tumours typically have molecular characteristic called microsatellite instability
Early onset colorectal cancer right sided at 40
Screening from 25 and every 2 years
What are some other high risk groups?
FH of CRC
IBD
Previous CRC
Previous adenomas
Who needs FIT test?
Asymptomatic screenings
Assess and triage symptomatic patients
