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%
Which groups are more likely to get colorectal cancer?
- the incidence increases with age
- it is more common in males
How is the mortality changing over time?
- mortality rates are decreasing over time due to more effective screening programmes and better treatments
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
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
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
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
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
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
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
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
Which parts of the colon are most commonly affected by colon cancer?
- tumours are much more common in the left colon** and **rectum
- around 1/3 occur in the rectum, 1/3 on the left side and 1/3 in the remainder of the colon
What are the 6 main red flag symptoms associated with colorectal cancer?
- rectal bleeding
- change in bowel habit / unable to fully empty bowels
- abdominal pain
- mucous PR
- anorexia
- weight loss
What signs of colorectal cancer might be present on examination?
- systemic signs of cancer, such as anaemia and weight loss
- abdominal mass / fullness
- mass, ulcer or stricture on rectal examination
What would be the next stage of investigation for someone presenting with red flag symptoms?
referral via the urgent 2 week-wait cancer referral pathway
- if patient is fit and well, they will have a colonoscopy / flexible sigmoidoscopy
- if they are less well, they will have a colorectal surgeon / gastro review within 14 days
if cancer is diagnosed, treatment must start within 62 days
What other screening programme has been introduced recently for younger individuals?
bowel screening scope (sigmoidoscopy)
- this is a one-off test to detect left-sided polyps offered at 55
- if it is normal, continue into bowel screening at 60
If abnormal tissue is seen during colonoscopy, what is done?
- a biopsy is taken at the point of colonoscopy to confirm the diagnosis
- this is the only test that can definitively diagnose the cancer
After diagnosis, why might a CT scan be performed?
- CT of the thorax, abdomen and pelvis is performed to stage the cancer and look for signs of metastasis
- this can measure the size of the tumour
- it is often performed prior to surgery
What is the definitive imaging modality used for colorectal cancer and why?
MRI is used for the pelvic staging of colorectal cancer
- soft tissue is easier to visualise on MRI compared to CT
- can assess nodal involvement, vascular invasion and how far the tumour extends outside of the bowel wall
What is the CRM?
circumferential resection margin
- this is the plane that the surgeons will resect around to ensure that the tumour is completely removed
- tumour involvement of the CRM affects treatment of these patients
What is the typical treatment for colon cancer?
- typically, all patients go straight to surgery
- this may be a hemicolectomy or anterior resection
- neoadjuvant chemotherapy prior to surgery is considered in those with advanced disease (T3/T4 or node positive)
How does the treatment for rectal cancer differ from colon cancer?
- neoadjuvant treatment prior to surgery is usually given to prevent the risk of recurrence
Low risk:
- typically go straight to surgery - anterior resection, APER or Hartmanns
Moderate risk:
- neoadjuvant treatment with radiotherapy to prevent recurrence prior to surgery
- surgery within 1 week of the course of radiotherapy
High risk:
- neoadjuvant therapy with radiotherapy + chemotherapy to shrink the tumour prior to surgery
- in these patients, there is involvement of the CRM
How is it decided whether a patient will have adjuvant chemotherapy following surgery for rectal cancer?
- low risk patients possess no benefit from adjuvant chemotherapy
- moderate risk patients have a small benefit from chemotherapy, and should be discussed within the MDT
- high risk patients have an absolute benefit from chemotherapy as they are at the greatest risk of recurrence
How does a carcinoembryomic antigen (CEA) test work?
- carcinoembryonic antigens are produced by some types of cancer, including bowel cancer
- the CEA test is carried out after surgery
- it measures the level of CEA in the blood to check how well the treatment is working and look for signs of recurrence
