Colorectal cancer

Question 1

Define colorectal cancer

Answer 1

Cancer involving the large intestine (colon and rectum)

Question 2

Where does the colon begin?

Answer 2

Ileo-caecal junction

Question 3

What are the 5 parts of the colon?

Answer 3

Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon

Question 4

What is the function of the colon?

Answer 4

Receives digested food
Absorbs water and electrolytes
Forms faeces

Question 5

What vessel supplies midgut-derived structures?

Answer 5

SMA

Question 6

What vessel supplies hindgut-derived structures?

Answer 6

IMA

Question 7

What is the blood supply of the ascending colon?

Answer 7

SMA

• ileocolic aa
• right colic aa

Question 8

What are the branches of the ileocolic artery?

Answer 8

Colic aa
Anterior caecal aa
Posterior caecal aa

Question 9

What is the blood supply of the transverse colon?

Answer 9

SMA

- middle colic aa

Question 10

What is the blood supply of the descending colon?

Answer 10

IMA

- left colic aa

Question 11

What is the blood supply of the sigmoid colon?

Answer 11

IMA

- sigmoid arteries

Question 12

What is the Marginal Artery of Drummond?

Answer 12

Anastomoses between SMA and IMA that provides collateral supply to the colon

Question 13

What is the lymphatic drainage of the colon?

Answer 13

SMN and IMN -> cisterna chyli -> thoracic duct

Question 14

What are the 2 major flexures of the rectum?

Answer 14

Sacral

Anorectal

Question 15

Give the blood supply of the rectum

Answer 15

IMA
- superior rectal
Internal iliac 
- middle rectal
Internal pudendal
- inferior rectal

Question 16

Discuss the epidemiology of colorectal cancer

Answer 16

> 65yo
W>B
M>F

Question 17

Name risk factors for colorectal cancer

Answer 17

>65yo
Smoking
Obesity
Diet (red meat, processed, alcohol)
IBD
Personal history of polyps of cancer

Question 18

Name screening modalities for colorectal cancer

Answer 18

Faecal occult blood test
Sigmoidoscopy
Colonoscopy

Question 19

What is the pathogenesis of colorectal cancer?

Answer 19

Sporadic

Inherited

Question 20

What are the 3 genetic pathways implicated in the pathogenesis of colorectal cancer?

Answer 20

1. Chromosomal instability
2. Microsomal instability
3. Serrated pathway

Question 21

Explain the chromosomal instability pathway

Answer 21

Inactivating tumour suppressor genes (APC)

Activating proto-oncogenes (KRAS)

Question 22

Explain the microsomal instability pathway

Answer 22

Inactivation of MMR genes (MLH1) due to epigenetic silencing via promoter hypermethylation

Question 23

Explain the serrated pathway

Answer 23

Proto-oncogene BRAF mutation

Question 24

How is colorectal cancer staged?

Answer 24

AJCC TNM staging

Modified Duke’s = old system

Question 25

Discuss the AJCC TNM staging of colorectal cancer

Answer 25

T1 - invades submucosa T2 - invades muscularis propria T3 - invades subserosa or non-peritonealized pericolic/perirectal tissue T4 - directly invades other structures or visceral peritoneum ``` N1 = 1-3 LN N2 = >3 LN ```

Question 26

Name suspicious symptoms that clinically suggest colorectal cancer

Answer 26

``` Significant weight loss Constipation Change in bowel habits PR bleeding Rectal mass Tenesmus Rectal pain ```

Question 27

How can complications of colorectal cancer present clinically?

Answer 27

``` Intestinal obstruction Perforation Peritonitis Abdominal pain Iron deficiency anemia Acute GI bleed ```

Question 28

How can colorectal cancer spread?

Answer 28

Lymphatic Hematogenous Contiguous Transperitoneal

Question 29

Name the most common sites of colorectal cancer metastases

Answer 29

LN Liver Lungs Peritoneum

Question 30

Where can tumours in the distal rectum metastasize to initially and why?

Answer 30

Lungs | Inferior rectal vv drains into IVC

Question 31

Name atypical symptoms of colorectal cancer

Answer 31

Pneumaturia | Fever of unknown origin

Question 32

Name investigations in colorectal cancer

Answer 32

``` Bloods - FBC, U+E, LFT, CEA, HIV Imaging - CXR - AXR Colonoscopy Staging CT ```

Question 33

Name treatment options for colorectal cancer

Answer 33

Chemotherapy Radiotherapy Surgical

Question 34

Name indications for adjuvant chemotherapy in colorectal cancer

Answer 34

Metastatic T3, T4 tumours Positive lymph nodes High risk features

Question 35

Discuss palliation in colorectal cancer

Answer 35

``` Analgesia Bowel obstruction surgery ERCP (obstructive jaundice) Psychologist Radiotherapy Chemotherapy ```

Question 36

How long is surveillance in colorectal cancer carried out for?

Answer 36

Minimum 5 years

Question 37

How do you perform surveillance in post-colorectal cancer patients?

Answer 37

Clinical Bloods CT scan Colonoscopy