Colorectal Cancer and Screening Flashcards
(65 cards)
1
Q
What is the epidemiology of CRC?
A
- 2nd leading cause of cancer death in the Western world
- 17,000 UK deaths per year
- 3rd commonest cancer diagnosis overall
- 2/3rds colonic cancer
- 1/3 rectal cancer
2
Q
What are 95% of CRCs?
A
Adenocarcinomas
3
Q
What are the risk factors for CRC?
A
- Sporadic cancers
- Familial risk
- Inheritable conditions : HNPCC, FAP
- IBD
4
Q
What are the risk factors for sporadic CRC?
A
- Age
- Male
- Previous adenoma/CRC
- Diet
- Obesity
- Lack of exercise
- Smoking
- Diabetes mellitus
5
Q
What diet choices can increase your risk of CRC?
A
- Decreased fire
- Decreased fruit and veg
- Decreased calcium
- Increased red meat
- Increased alcohol
6
Q
What do the majority of CRCs arise from?
A
Pre-existing polyps
7
Q
what are colorectal polyps?
A
- Protuberant growths that vary in histological types.
- They can be epithelial or mesenchymal and benign or malignant
8
Q
What is the origin of adenomas?
A
Epithelial
9
Q
What stage are adenomas?
A
- Benign
- Pre-malignant
10
Q
What are the 2 main histological types of adenomas?
A
- Tubular
- Villous
11
Q
What is the other histological type of adenoma?
A
Indeterminate tubulovillous
12
Q
How can adenomas present morphologically?
A
- Pedunculated
- Sessile
13
Q
What can affect the severity of an adenoma?
A
- Size
- Number
- Degree of dysplasia
- Villous architecture
14
Q
What are the 3 stages involved in the carcinoma sequence?
A
- Activation of oncogenes
- Loss of tumour suppressor gene
- Defective DNA repair pathway genes (microsatellite instability)
15
Q
What oncogenes are associated with CRC?
A
- KRAS
- CMYC
16
Q
What tumour suppressor genes are associated with CRC?
A
- APC
- p53
- DCC
17
Q
How does CRC present?
A
- Rectal bleeding
- Altered bowel opening
- Iron deficiency anaemia
- Palpable rectal or right lower abdominal mass
- Acute colonic obstruction if stenosing tumour
- Systemic symptoms of malignancy (weight loss, anorexia)
18
Q
What does presenting with iron deficiency anaemia suggest?
A
Right sided colonic malignancy
19
Q
When should rectal bleeding and altered bowel opening be investigated?
A
- Each symptom on its own >60years
- Combined >40 years
20
Q
What is the investigation of choice in CRC?
A
Colonoscopy
21
Q
What can also be carried out during colonoscopy?
A
- Tissue biopsies
- Therapeutic measures (polypectomy)
22
Q
What is preparation is required for a colonoscopy?
A
- Sedation
- Bowel preparation
23
Q
What are the risks when carrying out therapeutic interventions during colonoscopy?
A
- Perforation
- Bleeding
24
Q
What radiological imaging can be carried out when investigating CRC?
A
- Barium enema
- CT colonography (3D virtual colonoscopy)
- CT abdo/pelvis
25
What are the disadvantages of radiological imaging in CRC investigation?
- Ionising radiation
- Bowel preparation
- No histology
- No therapeutic intervention
26
What can malignant cell invade?
Local tissues, metastasise to lymph odes or via blood to other solid organs
27
What investigations are carried out in the staging process?
- CT scan chest/abdomen/pelvis
- MRI scan for rectal tumours
- PET scan / rectal endoscopic ultrasound in selected cases
28
What are the 2 classifications for staging?
- TNM
| - Dukes classification
29
What are the stages in the Duke's classification
- A: tumour confined to mucosa
- B: tumour extended through mucosa to muscle layer
- C: involvement of lymph nodes
- D: distant metastatic spread
30
What is the basis of therapy in CRC?
Surgery
31
What does the operative procedure performed depend on?
- Site
- Size
- Stage of tumour
32
What are the 2 ways in which surgery can be carried out?
- Laparotomy
| - Laparoscopic
33
How are Dukes A and "cancer polyps" treated?
Endoscopic or local resection
34
What other procedures can be carried out during surgery for CRC?
- Stoma formation
- Removal of lymph nodes for histological analysis
- Partial hepatectomy for metastases
35
When is chemotherapy given as a treatment?
- Adjuvant
- Dukes C, Dukes B
- +ve LN histology
- Mops up metastases
36
What chemotherapy agents are used?
5FU (flurouracil) and other agents
37
When is radiotherapy given as a treatment for CRC?
- Rectal cancer only
| - Neo-adjuvant +/- chemotherapy to control primary tumour prior to surgery
38
What palliative care can be given for advanced disease?
- Chemotherapy
| - Colonic stenting to prevent colonic obstruction
39
How can the outlooks be improved?
- Prevention
| - Screening
40
What is the aim of CRC population screening?
Detect pre-malignant adenomas and early cancers in the general population
41
What are the modalities of screening?
-Faecal occult blood test (FOBT)
-Faecal immunochemical test (FIT)
-Flexible sigmoidoscopy
-Colonoscopy
CT colongraphy
42
Describe the Scottish bowel screening programme.
- Rolled out in 2007
- Age 50-74 years
- FOBT every 2 years
- If FOBT positive then colonoscopy
43
What has the Scottish bowel screening programme resulted in?
- Stage shift in detected cancers
| - Reduction in the relative risk of CRC mortality
44
What high risk groups are screened for CRC?
- Heritable conditions (FAP, HNPCC)
- IBD
- Familial risk
- Previous adenomas/CRC
45
FAP
Familial adenomatous polyposis
46
HNPCC
Hereditary non-polyposis colorectal cancer
47
What type of condition is FAP?
Autosomal dominant
48
What occurs in FAP?
Multiple adenomas throughout colon
49
What causes FAP?
Mutation of the APC gene on chromosome 5
50
What is the risk of malignancy with FAP?
High risk of malignancy in early adulthood, in almost all cases by age 40 if untreated
51
What is the screening provided to those with FAP?
Annual colonoscopy from age 10-12 years
52
What prophylaxis is offered to those with FAP?
Proctocolectomy usually age 16-25
53
What are the extracolonic manifestations of FAP?
- Benign gastric fundic cystic hyperplastic
- Duodenal adenomas with periampullary cancer
- Desmoid tumours
- Congenital retinal hypertrophy of the pigment epithelia (CHRPE)
54
What NSAID chemoprevention is there for FAP?
Sulindac reduces polyp number and prevents recurrence of higher grade adenomas in the retained rectal segment
55
What type of condition is HNPCC?
Autosomal dominant
56
What causes HNPCC?
Mutation in DNA mismatch repair genes
57
What do tumours as a result of HNPCC typically have?
A characteristic called microsatellite instability- frequent mutations in short repeated DNA sequences
58
What can HNPCC predispose you to?
- Early onset CRC (40s) right sided
| - Associated with cancers at other sites : endometrial, genitourinary, stomach, pancrease
59
How is HNPCC diagnosed?
- Clinical criteria (Amsterdam/Bethesda)
| - Genetic testing
60
What is the screening provided to those with HNPCC?
- Screening from age 25
| - 2 yearly colonoscopy
61
What screening is provided for those with IBD?
Index surveillance colonoscopy 10 years post diagnosis then dependent on duration, extent and activity of inflammation and presence of dysplasia
62
What is the screening provided for previous CRC patients?
5 yearly colonoscopy
63
What is the screening dependent on for those with previous adenomas?
- Number of polyps
- Size
- Degree of dysplasia
64
What is the screening provided for those with familial history of CRC in the high moderate risk group?
- CRC in 3 FDR none <50 years
- CRC in 2 FDR mean age <60 years
- 5 yearly colonoscopy from age 50
65
What is the screening provided to those with familial history of CRC in the low moderate risk group?
- CRC in 2FDR >60 years
- CRC in 1 FDR <50 years
- Once only colonoscopy at age 55 years
