Colorectal Cancer and Screening Flashcards
What fraction of colorectal cancers are colonic and what fraction are rectal?
Two thirds colonic, one third rectal
What percentage of colorectal cancers are associated with underlying IBD?
1%
What percentage of colorectal cancers have an associated familial risk?
10%
What are the risk factors for colorectal cancers?
Age Male Previous adenoma/CRC Diet Obesity Lack of exercise Smoking Diabetes mellitus Polyps
What do the majority of colorectal cancers arise from?
Pre-existing polyps
The majority of colorectal polyps are
adenomas
What are polyps?
Benign, pre malignant, epithelial in origin, small growths
What are the histological types of polyps?
Tubular (75%)
Villous (10%)
Tubulovillous (15%)
What is the basic pathogenesis of the development from polyps into colorectal carcinoma?
Normal epithelium
- > small adenoma
- > large adenoma
- > invasive adenocarcinoma
The activation of what oncogenes causes the loss of tumour suppressor genes?
k-ras
c-myc
What is the typical presentation of colorectal carcinoma?
Persistent rectal bleeding
Altered bowel opening - particularly diarrhoea
Iron deficiency anaemia
Palpable rectal or lower right abdominal mass
Acute colonic obstruction - if stenosing tumour
Systemic symptoms e.g. weight loss
What are the sites of colorectal cancer?
Ascending colon Transverse colon Descending colon Rectum Anus Other
What is the aim of population screening for bowel cancer?
To detect pre-malignant adenomas or early cancers in the general population
What tests might be used to detect pre-malignancy/early malignancy in the general population through screening programmes?
Faecal occult blood test (FOBT)
Faecal immunochemical test (FIT)
What other investigations might be done to detect pre-malignancy/early malignancy in bowel cancer?
Flexible sigmoidoscopy
Colonoscopy
CT colonography
