Colorectal cancer

Question 1

Colorectal cancer epidemiology

Answer 1

2nd leading cause of cancer death in western world

Question 2

what is the ratio of colonic to rectal involvement with colorectal cancer?

Answer 2

2/3 colonic and 1/3 rectal

Question 3

what percentage of colorectal cancer cases are sporadic?

Answer 3

85%

Question 4

name some inheritable conditions that lead to colorectal cancer

Answer 4

HNPCC (5%)
FAP (<1%)
other CRC syndromes

Question 5

Risk factors for sporadic cases (8)

Answer 5

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

Question 6

What do the majority of colorectal cancers arise from?

Answer 6

pre-existing polyps

Question 7

describe colorectal polyps

Answer 7

protuberant growths

variety of histological types

epithelial or mesenchymal cells (stem cells)

benign or malignant

Question 8

Describe adenomas

Answer 8

benign, pre-malignant

epithelial in origin

2 main histological types - tubular villous or indeterminate tubulovillous

Question 9

what determines whether a lesion is high risk? (4)

Answer 9

its size
number
degree of dysplasia villous architecture

Question 10

How does an adenoma progress to carcinoma?

Answer 10

normal epithelium – mutations – small adenoma – k-ras or c-myc activation – large adenoma – more mutuations – invasive adenocarcinoma – metastases

Question 11

which oncogenes are involved with colorectal cancer

Answer 11

k-ras

c-myc

Question 12

Presentation of colorectal cancer (7)

Answer 12

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

Question 13

Investigation options for colorectal cancer?

Answer 13

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

Question 14

Risks of colonoscopy? (2)

Answer 14

perforation

bleeding

Question 15

Staging investigations for colorectal cancer?

Answer 15

CT scan chest/abdomen/pelvis

MRI scan for rectal tumours

PET scan / rectal endoscopic ultrasound in selected cases

Question 16

TNM staging roughly explained

Answer 16

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

Question 17

Surgery as treatment for colorectal cancer

Answer 17

80% patients have surgery

Dukes A and ‘cancer polyps’ endoscopic or local resection

procedure depends on site, size and stage of tumour

Question 18

What is surgery to put a stoma in place called?

Answer 18

colostomy - permanent/temporary

Question 19

For advanced disease, what does palliative care involve?

Answer 19

chemotherapy

colonic stenting to prevent colonic obstruction

Question 20

Who is radiotherapy given to?

Answer 20

rectal cancer patients only

neodjuvant with or without chemo is given to control primary tumour prior to surgery

Question 21

Chemotherapy in colorectal cancer

Answer 21

mops up micrometastases
adjuvant - given after surgery to try make it more successful

agents like fluorouracil are used

Question 22

What is Duke’s staging for colorectal cancer?

Answer 22

similar to TNM, it is just another staging criteria

Duke’s stages are A, B, C and D

Question 23

Give examples of prevention methods that can be done to reduce risk of colon cancer?

Answer 23

exercise most days
BMI of 18.5-25 kg/m^2 maintained
5 a day
no smoking

Question 24

Is there screening for bowel cancer on the NHS?

Answer 24

yes, once you reach 55

FOBT every 2 years - if positive - colonoscopy

Question 25

what screening methods are there? (5)

Answer 25

Faecal occult blood test (FOBT) / Faecal immunochemical test (FIT) - home stool test checking for blood.

Flexible Sigmoidoscopy

Colonoscopy

CT Colonography

Question 26

Screening is available for high risk groups. Give some examples of high risk groups?

Answer 26

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

Question 27

Familial adenomatous polyposis

Answer 27

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

Question 28

Drug treatment for FAP

Answer 28

NSAIDs chemoprevention - reduce number of polyps and prevents recurrence of higher grade adenomas

Question 29

Describe hereditary non-polyposis colorectal cancer

Answer 29

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

Question 30

Diagnosis of hereditary non-polyposis colorectal cancer

Answer 30

use clinical criteria called Amsterdam or Bethesda or genetic testing

Question 31

describe the Amsterdam criteria

Answer 31

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

Question 32

New FIT- based model for detection of colorectal disease

Answer 32

screening asymptomatic individuals for colorectal cancer or assessing and triage of symptomatic patients

both get a FIT

then colonoscopy

Question 33

What value indicates a positive FIT test

Answer 33

more than or equal to 10 ug Hb/g