Colorectal Cancer and Screening Flashcards
What type of cancer is colorectal cancer most commonly?
- 95% adenocarcinomas
- 2 thirds colonic, 1 third rectal
What are the comon ways colorectal cancer arises?
- Most (85%) are sporadic with no familial/genetic influence
- 10% have a familial risk
- Inheritable conditions: HNPCC (5%), FAP (<1%), other CRC syndromes
- 1% associated with underlying Inflammatory Bowel Disease (IBD)
What are risk factors for sporadic cases of colorectal cancer?
Age
Male gender
Previous adenoma/CRC
Environmental influences:
–Diet (reduced fibre, reduced fruit & veg,
reduced calcium, increased red meat, increased alcohol,)
–Obesity
–Lack of exercise
–Smoking
–Diabetes Mellitus
What do the majortiy of colorectal cancers arise from?
Existing polyps
- protuberant growths
- variety of histological types
- epithelial or mesenchymal
- benign or malignant
What is the origin of adenomas?
Epithelial origin
What are the two histological types of adeomas?
•2 main histological types – tubular (75%), villous (10%), indeterminate tubulovillous (15%)
What are the oncogenes responsible for carcinoma of the colon?
k-ras, c-myc
What are the tumour suppressor genes that are lost in the process of carcinoma formaiton?
– APC, p53, DCC
What is the presentation of colorectal cancer?
Rectal bleeding
Altered bowel opening - diarrhoea
Iron deficiency anaemia
Iron Deficiency Anaemia men of any age and non-menstruating women (more likely to have right sided colonic malignancy)
Palpable rectal or right lower abdominal mass
Acute colonic obstruction if stenosing tumour
Systemic symptoms of malignancy: Weight loss, Anorexia
How do alarm features come in play when diagnosing colorectal cancer?
Poor sensitivity and specificity for diagnosis of colorectal cancer
What are the investigations for colorectal cancer?
Colonoscopy
Radiological imaging: barium enema, CT colonography, CT of abdomen and pelvis
What are benefits of colonoscopy?
Allows tissue biopsies to be taken
Can be used therapeutically (polypectomy)
What are the risks associated with colonoscopy?
Perforation
Bleeding
What are the disadvantages of radiological imaging?
Ionising radiation
No histology
No therapeutic intervention
What are the staging investigations for colorectal cancer?
CT scan chest/abdomen/pelvis
MRI scan for rectal tumours
PET scan / rectal endoscopic ultrasound in selected cases
What is the TNM staging for colorectal cancer?
T1-T4 local disease progression
N0 – N1 lymph nodes involvement
M0 – M1 distant metastases
What is the Duke’s classification for colorectal cancer staging?
A – Tumour confined to mucosa
B – Tumour extended through mucosa to muscle layer
C – Involvement of lymph nodes
D - Distant metastatic spread
What is the treatment for colorectal cancer?
Surgery in 80% of cases
Dukes A and ‘cancer polyps’: endoscopic or local resection
What else might be removed during a colestomy?
Lymph nodes for histological analysis
Partial hepatectomy for metastases
What is involved in palliative care of colorectal cancer?
Chemotherapy, colonic stenting to prevent colonic obstruction
When is chemotherapy administered?
Advanced disease
Used as an adjuvant - to suppress secondary tumour formation
Used in cases of Dukes C and Dukes B
Used in positive cases of lymph node involvement
When is radiotherapy indicated?
Rectal cancer only
‘neoadjuvant’ +/- chemotharapy to control primary tumour prior to surgery
What are prevention measures against getting colorectal cancer?
30 minutes of physical activity most days
Maintain healthy BMI (18.5 - 25)
Eat 5 or more portions of fruit or veg a day
Not to smoke
