Big 4 - Colorectal Cancer Flashcards
What is the incidence of bowel cancer?
What is the survival after 1 year and 5 years like?
1 in 20 people will get bowel cancer during their life time
- the 1 year survival is 75-80% which is considered to be quite good
- the 5 year survival is 60%
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Which groups are more likely to get colorectal cancer?
- the incidence increases with age
- it is more common in males
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How is the mortality changing over time?
- mortality rates are decreasing over time due to more effective screening programmes and better treatments
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How is colorectal cancer staged?
TNM system
- T stage is how far the tumour has eroded through the bowel wall
- N stage is based on the number of lymph nodes involved
- M stage is based on the extent of metastases and the organs involved
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How can the T stage further be subdivided from T1 to T4?
Tis:
- this is carcinoma in situ - the tumour is only within the mucosa
T1:
- the tumour is only in the inner layer of the bowel
T2:
- the tumour has grown into the muscular layer of the bowel wall
T3:
- the tumour has grown into the outer lining of the bowel wall but has not grown through it
T4a:
- the tumour has grown through the outer lining of the bowel wall and into the peritoneum
T4b:
- the tumour has grown through the outer lining of the bowel wall and into nearby organs
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How can the N stage be further subdivided into N0-N2?
N0:
- there are no lymph nodes containing cancer cells
N1a:
- there are cancer cells in 1 nearby lymph node
N1b:
- there are cancer cells in 2 or 3 nearby lymph nodes
N1c:
- the nearby lymph nodes do not contain cancer, but there are cancer cells in tissue near the tumour
N2a:
- there are cancer cells in 4 to 6 nearby lymph nodes
N2b:
- there are cancer cells in 7 or more nearby lymph nodes
How can the M stage be further subdivided?
M0:
- the cancer has not spread to other organs
M1a:
- the cancer has spread to 1 distant site / organ but not to the peritoneum
M1b:
- the cancer has spread to 2** distant sites / organs but **not to the peritoneum
M1c:
- the cancer may have spread to distant organs and has spread to the peritoneum
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How does the stage that the cancer is detected influence survival rate?
- survival rates are influenced by the stage at the time the cancer is picked up
- there is a much better prognosis if a cancer is picked up early
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How does bowel cancer develop?
- there is a progression from benign polyps to invasive cancer
- the tumours develop through a multistep process involving histological, morphological and genetic changes that accumulate over time
- polyps are well-demarcated and round, whereas tumours are much more invasive
- polyps are removed to prevent later development of cancer
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What types of polyps are at a higher risk for developing into colorectal cancer?
What other factors increase this risk?
- adenomatous polyps can change into cancer so are called a pre-cancerous condition
- hyperplastic and inflammatory polyps are not pre-cancerous
- polyps >1cm are more likely to become cancer
- if more than 3 polyps are found, this increases the risk
- if dysplasia is seen in the polyp after it has been removed
- the cells look abnormal, but they have not yet become cancer
How can colorectal cancer spread once it forms within a polyp?
the cancer will grow from the polyp into the wall of the colon / rectum over time
- the cancer starts in the mucosa (innermost layer) of the bowel and grows outward through some or all of the other layers
- when cancer cells are in the wall, they can grow into blood or lymph vessels, allowing them to travel to lymph nodes or distant parts of the body
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What is the most common type of colorectal cancer?
most colorectal cancers are adenocarcinomas
- these start in the cells that make mucus to lubricate the inside of the colon and rectum
- adenocarcinomas always form in glandular tissue that lines certain internal organs and releases substances into the body
What are the risk factors associated with colorectal cancer?
- obesity
- lack of physical activity
- diet high in red / processed meats
- smoking
- excessive alcohol consumption
- advancing age
- personal history of inflammatory bowel disease
- personal history of adenomatous polyps or cancer
- family history of adenomatous polyps or cancer
- inherited syndromes - Lynch syndrome and FAP
What is Lynch syndrome caused by?
(hereditary non-polyposis colon cancer)
What other conditions can this cause?
- caused by a defect in the MLH1, MSH2 or MSH6 gene that usually help to repair damaged DNA
- cancers linked to this syndrome develop when a person is relatively young
- there may be polyps present, but usually only a small amount
- also strongly linked to endometrial cancer, as well as ovarian, stomach, pancreatic, kidney, prostate, breast…and more
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What causes familial adenomatous polyposis (FAP)?
When do these people tend to develop colon cancer and why?
- caused by changes in the APC gene that a person inherits from their paretns
- 100s-1000s of polyps develop in the colon and rectum, starting as early as 10-12 years
- cancer usually develops in 1 or more of the polyps by the age of 20
- by age 40, nearly all people will have colon cancer if their colon hasn’t been removed
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