Colorectal Flashcards
What locations are covered by “colorectal” cancers?
rectal, sigmoid, transverse colon, ascending colon and caecum, descending colon (respectively highest to lowest average)
What are the 3 types of colorectal cancers?
sporadic
hereditary non-polyposis colorectal carcinoma (HNPCC)
familial adenomatous polyposis
How do sporadic colorectal cancers come about?
series of genetic mutations, for an example more than half show allelic loss of APC gene
What is HNPCC?
aka Lynch syndrome
autosomal dominant condition, most common form of inherited colon cancer
- activation of K-ras oncogene, deletion of P53 and DCC tumour suppressor gene lead to invasive carcinoma
- 90% proximal colon, poorly differentiates and highly aggressive
- higher risk of endometrial cancers!
How is Lynch syndrome diagnosed?
(Amsterdam criteria)
- at least 3 family members with colon cancer
- the cases span at least two generations
- at least one case diagnosed before the age of 50 years
What is familial adenomatous polyposis? (FAP)
autosomal dominant which leads to formation of hundreds of polyps by age 30-40
- pt inevitable develop carcinoma due to mutation in tumour suppressor gene called adenomatous polyposis coli gene (APC) on chromosome 5
What does FAP increase your risk of?
duodenal tumours, variant of this called Gardner’s syndrome can also feature osteomas of skull and mandible, retinal pigmentation, thyroid carcinoma and epidermoid cysts on the skin
What are the risk factors of developing colorectal cancers?
- sporadic
- increasing age
- male
- family history
- iBD
- low fibre diet
- high processed meat intake
- smoking
- excess alcohol
How might colorectal cancers present?
change in bowel habits
rectal bleeding
abdominal pain or discomfort
unexplained WL
anaemia
bowel obstruction
How might right sided colorectal tumours present?
abdominal pain, iron-deficiency anaemia, palpable mass in right iliac fossa, often present late
*Right sided cancers have histology and morphology which is flatter than the left side which is more polyp like hence occlude faster
How might left sided colorectal tumours present?
rectal bleeding, change in bowel habit, tenesmus, palpable mass in left iliac fossa or on PR exam
How might you investigate colorectal cancer suspicions?
routine bloods - FBC microcytic, ferritin and iron levels, LFT and clotting
FIT testing
colonoscopy and sigmoidoscopy
biopsy
CT staging
When would you refer someone for FIT testing?
- abdo mass, change in bowel habits, iron deficiency anaemia, over 40 with unexplained weight loss or abdominal pain
- under 50 with tectal bleeding and abdo pain or weight loss
- over 50 with rectal bleeding, abdominal pain, weight loss
- 60 and over with anaemia even without iron deficiency
What is the colorectal screening pathway in the UK?
❕ every 2 years to all men and women aged 60-74 through post
- uses faecal occult blood which uses antibodies to recognise human haemoglobin
- if abnormal offered colonoscopy
How are colorectal cancers staged?
Dukes staging
* according to extent of disease through layers of intestine, mets for 5 year survival
- carcinoembryonic antigen (CEA)
- poor sensitivity and specificity but used to monitor disease progression
- CT chest, abdomen and pelvis
- entire colon evacuated with colonoscopy or CT colonography
- mesorectum evaluated under MRI if below peritoneal reflection
- TNM staging
