Colorectal cancer Flashcards
What is a polyp
It a protrusion above an epithelial surface (it is a tumour/swelling)
What are the 4 main classes of polyps ?
- Adenoma
- Serrated polyp
- Polypoid carcinoma
- Other
Need histopathology to tell them apart!
What do the majority of colorectal cancers arise from ?
Pre-existing adenomatous polyps
What is the main type of colorectal cancer ?
Adenocarcinoma
What are the risk factors for developing colorectal cancer?
- Older age - ¾ of cases occurring in people over age of 65
- Low intake of fibre
- High intake of fat, sugar, alcohol, red meat, processed meats
- Obesity
- Smoking
- Lack of physical exercise
- Long-standing IBD - UC more than crohns
What are the genetic mutations which increase the risk of colorectal cancer ?
- Mutations in APC ( adenomatous polyposis coli)
- Mutations of p53 gene
What are the 2 main familial conditions which greatly increase the risk of colorectal cancer ?
- Familial adenomatous polyposis (FAP)
- Hereditary non-polyposis colorectal carcinoma - HNPCC (Lynch syndrome)
What is HNPCC and what mutations cause it
- It is an autosomal dominant condition and is the most common form of inherited colorectal cancer.
- Around 90% of patients will develop cancers
- It is most commonly caused by MSH1/2 mutations
What criteria can be used to help recognise HNPCC?
The Amsterdam criteria are sometimes used to aid diagnosis:
- 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 other cancers is HNPCC condition associated with causing ?
Gastric and endometrial carcinoma
What is the management/screening required for someone with HNPCC?
- Colonoscopy every 1-2 years from age 25
- Consideration of prophylactic surgery
- Extra colonic surveillance recommended
What can patients with lynch syndrome take to help reduce the risk of colorectal cancer ?
Daily aspirin for > 2 years
What is FAP and what mutations cause it
- A rare autosomal dominant condition which leads to the formation of hundreds of polyps by the age of 30-40 years. Patients inevitably develop carcinoma.
- Due to Mutation of APC gene
What other cancers is FAP associated with ?
Desmoid tumours and thyroid carcinoma
What is the management/screening required for someone with FAP?
- Annual flexible sigmoidoscopy from 15 years
- If no polyps found then 5 yearly colonoscopy started at age 20
- Polyps found = resectional surgery
Patients generally have a total colectomy with ileo-anal pouch formation in their twenties.
What type of colorectal cancers does HNPCC and FAP cause ?
- HNPCC causes mucinous tumours
- FAP causes adenocarcinomas
What are the signs/symptoms of a left-sided (rectum, sigmoid, descending) colorectal cancer ?
- Rectal bleeding
- Feeling of incomplete emptying
- Worsening constipation/obstruction
What are the signs/symptoms of a right-sided (Caecum, Ascending) colorectal cancer ?
- Unexplained Iron deficiency anaemia - persistent tiredness
- A persistent and unexplained change in bowel habit
- Unexplained weight loss
- Abdominal pain (colicky in nature)
- Lump in the abdomen
When should someone excluding for screening be offered faecal occult blood testing (FOBT)?
- ≥ 50 years with unexplained abdominal pain OR weight loss
- < 60 years with changes in their bowel habit OR iron deficiency anaemia
- ≥ 60 years who have anaemia even in the absence of iron deficiency
When should patients be referred urgently to the colorectal services for investigation and what should be done ?
- ≥ 40 years with unexplained weight loss AND abdominal pain
- ≥ 50 years with unexplained rectal bleeding
- ≥ 60 years with iron deficiency anaemia OR change in bowel habit
- Tests show occult blood in their faeces on FOBT
Should be seen urgently (within 2 weeks) for colonoscopy
What are the 2 screening tests offered in scotland for colorectal cancer ?
- Faecal Immunochemical Test (FIT) screening - this is the FOBT offered to people aged 50-74 every 2 years.
- Flexible sigmoidoscopy screening - Offered to 55 year-olds (this is a one off screen to detect and treat hopefully reducing rates of future cancer)
What can be used as an alternative to colonoscopy to diagnosed colorectal cancer ?
CT colonography
Following diagnosis of colorectal cancer what needs to be done ?
The pathology sample is sent to histopathology
Cancer staging needs to be done:
- CT chest/abdo/pelvis
- MRI for rectal cancers
This is followed by MDT review and decision for Surgery (hopefully curative or paliation treatment
What are the common sites of metastasis for colorectal cancer ?
- Direct spread - Mesorectum, Peritoneum,Other organs
- Lymphatic spread - mesenteric nodes
- Blood borne spread - to the Liver and Lungs
