Colorectal Cancer and Screening Flashcards
Is colorectal cancer a common cause of death?
Yeah
Second leading cause of cancer death in the western world (3rd commonest cancer overall)
Ooft
Risk factors for colorectal cancer?
Age Being male Smoking Previous adenoma/colorectal cancer Genetics - about 10% have familial risk Inflammatory Bowel Disease Lifestyle factors
Lifestyle related risks for colorectal cancer?
Diet
- low fibre, low fruit & veg, low calcium
- High red meat, fat and alcohol
Obesity
lack of exercise
Smoking
Diabetes MellitusHow do most colorectal cancers arise?
Majority arise from pre-existing polyps (usually adenomas)
What are adenomas? Types?
Describe a high risk adenoma
They are benign, pre-malignant epithelial growths. Three main types - tubular (75%), villous (10%) & tubulovillous
High risk lesions are large, have a high degree of dysplasia and villous architecture
Why do adenomas develop instead of just cancerous growths from the start?
Because adenomas mark stages where one or two genes regulating cell growth have been mutated, but there is still a line of control (multi-hit hypothesis)
Once all regulatory genes are mutated a carcinoma develops
Oncogenes and tumour suppressors regulating colorectal cancer formation?
Oncogenes: K-ras, c-myc
Suppressors: APC, p53, DCC
Presentation of colorectal cancer?
Rectal bleeding (more LS) Iron deficiency anaemia (more often right sided malignancy) Palpable rectal/right lower abdominal mass Colonic obstruction Cancer symptoms (weight loss etc.) Tenesmus (more LS)
First line investigation for suspected colorectal cancer?
Colonoscopy
Advantages of colonoscopy?
Allows biopsy to be taken
Can be therapeutic too - polypectomy (remove polyps during procedure)
Radiological investigations for suspected colorectal cancer?
CT colonography
CT abdomen/pelvis
Barium enema
Investigations for staging of colorectal cancer?
CT scan (chest/abdomen/pelvis)
MRI scan (rectal tumours)
PET scan
Rectal EUS (selected cases)
Treatment of colorectal cancer?
Surgery to remove infected part of bowel
May need to have stoma formed
Chemotherapy and radiotherapy
What is a stoma?
Opening in the abdomen that can be connected to digestive/urinary system to allow passage of waste
How are chemo and radiotherapy used in colorectal cancer?
Chemo often given adjuvantly to stop formation of secondary tumours
Both can be give neo-adjuvantly to control cancer before surgery
How is the prognosis for colorectal cancer greatly improved?
Early detection - screening
Screening modalities available for colorectal cancer?
Colonoscopy
Faecal occult blood test (FOBT)
Faecal immunochemical test (FIT)
Flexible sigmoidoscopy
CT colonography
Describe the Scottish Bowel Screening Program
For people age 50-74 years
- FOBT every 2 years
- If FOBT positive - colonoscopy
15% reduction in relative risk of colorectal cancer mortality
Advantages of the Faecal immunochemical test?
Easy, automated - user friendly
Flexibility - don’t have to only have every 2 years, if predisposed can test more often - reduce interval cancer rate
Also FOBT has lower positivity in women, unlike FIT
High risk groups for colorectal cancer?
Heritable conditions
- familial adenomatous polyposis (FAP)
- HNPCC (hereditary non-polyposis colorectal cancer)
IBD patients
Previous adenomas/colorectal cancer
What is familial adenomatous polyposis (FAP)?
Autosomal dominant condition causing proliferation of adenomas throughout colon (95% have >100 by age 35)
High risk of malignant change
Usually give annual colonoscopy from age 10-12 years
Management of FAP?
Screening for colorectal cancer
NSAIDs chemoprevention - Sulindac reduced polyp number and prevents recurrent higher grade adenomas
What is HNPCC?
hereditary non-polyposis colorectal cancer
Lynch - 1 inactive MMR gene
Autosomal dominant condition, causes tumours to have microsatellite instability - frequent mutations in short repeated segments observed
Susceptible to right sided colorectal cancer (early onset - usually in 40s)
Management of HNPCC?
Screening from age 25
Colonoscopy every 2 years
