Colorectal cancer Flashcards
Colorectal cancer epidemiology
2nd leading cause of cancer death in western world
what is the ratio of colonic to rectal involvement with colorectal cancer?
2/3 colonic and 1/3 rectal
what percentage of colorectal cancer cases are sporadic?
85%
name some inheritable conditions that lead to colorectal cancer
HNPCC (5%)
FAP (<1%)
other CRC syndromes
Risk factors for sporadic cases (8)
Age
Male>F
Previous adenoma/CRC
Environmental influences:
- Diet (decreased fibre, decreased fruit & veg,
decreased calcium, increased red meat, increased alcohol,) - Obesity
- Lack of exercise
- Smoking
- Diabetes Mellitus
What do the majority of colorectal cancers arise from?
pre-existing polyps
describe colorectal polyps
protuberant growths
variety of histological types
epithelial or mesenchymal cells (stem cells)
benign or malignant
Describe adenomas
benign, pre-malignant
epithelial in origin
2 main histological types - tubular villous or indeterminate tubulovillous
what determines whether a lesion is high risk? (4)
its size
number
degree of dysplasia villous architecture
How does an adenoma progress to carcinoma?
normal epithelium – mutations – small adenoma – k-ras or c-myc activation – large adenoma – more mutuations – invasive adenocarcinoma – metastases
which oncogenes are involved with colorectal cancer
k-ras
c-myc
Presentation of colorectal cancer (7)
Rectal bleeding (especially if mixed in with stool)
Altered bowel opening to loose stools >4 weeks
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
Investigation options for colorectal cancer?
colonoscopy - 1st choice, allows tissue biopsies to be taken. Can be therapeutic as well as diagnostic (polypectomy)
radiology - barium enema, CT colonography, CT abdo/pelvis
Risks of colonoscopy? (2)
perforation
bleeding
Staging investigations for colorectal cancer?
CT scan chest/abdomen/pelvis
MRI scan for rectal tumours
PET scan / rectal endoscopic ultrasound in selected cases
TNM staging roughly explained
T1 - confined to submucosa
T2
T3 - confined to serosa
T4 - invading other structures
N0 - no tumour involvement in regional lymph nodes
N1 - 3 L.N’s
N2 - 4+ L.N
M0 - no metastases
M1 - metastases
Surgery as treatment for colorectal cancer
80% patients have surgery
Dukes A and ‘cancer polyps’ endoscopic or local resection
procedure depends on site, size and stage of tumour
What is surgery to put a stoma in place called?
colostomy - permanent/temporary
For advanced disease, what does palliative care involve?
chemotherapy
colonic stenting to prevent colonic obstruction
Who is radiotherapy given to?
rectal cancer patients only
neodjuvant with or without chemo is given to control primary tumour prior to surgery
Chemotherapy in colorectal cancer
mops up micrometastases
adjuvant - given after surgery to try make it more successful
agents like fluorouracil are used
What is Duke’s staging for colorectal cancer?
similar to TNM, it is just another staging criteria
Duke’s stages are A, B, C and D
Give examples of prevention methods that can be done to reduce risk of colon cancer?
exercise most days
BMI of 18.5-25 kg/m^2 maintained
5 a day
no smoking
Is there screening for bowel cancer on the NHS?
yes, once you reach 55
FOBT every 2 years - if positive - colonoscopy
what screening methods are there? (5)
Faecal occult blood test (FOBT) / Faecal immunochemical test (FIT) - home stool test checking for blood.
Flexible Sigmoidoscopy
Colonoscopy
CT Colonography
Screening is available for high risk groups. Give some examples of high risk groups?
Patients with:-
heritable conditions like FAP (familial adenomatous polyposis) or HNPCC (hereditary non-polyposis colorectal cancer)
Inflammatory bowel disease
Familial risk
Previous adenomas/Colorectal cancer
Familial adenomatous polyposis
Autosomal dominant condition
Can get it very young - 50% by age 15
high risk of malignant change in early adulthood esp if untreated
screening - annual colonoscopy from age 10-12 years
prophylactic proctocolectomy 16-25 years - surgical removal of the rectum and all or part of the colon
Drug treatment for FAP
NSAIDs chemoprevention - reduce number of polyps and prevents recurrence of higher grade adenomas
Describe hereditary non-polyposis colorectal cancer
Autosomal dominant condition
Caused by a mutation in DNA mismatch repair (MMR) genes e.g MLH1 and MSH2
usually leads to early onset colorectal cancer (40s) - right sided
related to other cancers like endometrial, stomach, pancreas
Diagnosis of hereditary non-polyposis colorectal cancer
use clinical criteria called Amsterdam or Bethesda or genetic testing
describe the Amsterdam criteria
3 or more relatives with an associated cancer (colorectal cancer, or cancer of the endometrium, small intestine, ureter or renal pelvis);
2 or more successive generations affected;
1 or more relatives diagnosed before the age of 50 years
1 should be a first-degree relative of the other two; FAP should be excluded in cases of colorectal carcinoma
Tumors should be verified by pathologic examination
New FIT- based model for detection of colorectal disease
screening asymptomatic individuals for colorectal cancer or assessing and triage of symptomatic patients
both get a FIT
then colonoscopy
What value indicates a positive FIT test
more than or equal to 10 ug Hb/g
