29 - colorectal cancer

risk factors for colorectal cancer

family history

familial adenomatous polyposis (FAP)

hereditary nonpolyposis colorectal cancer (HNPCC)

IBD

increased age

diet high in red meat, low in fibre, low in fruit and veg, calcium

alcohol

smoking

what is FAP

autosomal dominant condition involving malfunctioning of tumour suppressor genes called adenomatous polyposis coli (APC)

- results in polyps in large intestine

- potential to become cancerous

-screening annual colonoscopy from age 10-12 years

what is HNPCC

autosomal dominant condition resulting in mutations in DNA mismatch repair (MMR) genes

- patients at high risk of cancer

-screening from age 25 → 2 yearly colonoscopy

what do majority of colorectal cancers arise from

polyps

adenoma to carcinoma in the colon - molecular aspect

activation of oncogene - k-ras or c-myc

loss of tumour suppressor genes - APC, p53, DCC

defective DNA repair pathways - microsatellite instability

ALL LEAD TO CELL GROWTH PROLIFERATION APOPTOSIS

red flag symptoms that may make you consider colorectal cancer

changes in bowel habit - usually more diarrhoea

unexplained weight loss

rectal bleeding - can be mixed with stool

unexplained abdominal pain

iron deficiency anaemia

palpable abdominal or rectal mass upon examination

NICE guidelines for referral in suspected colorectal cancer

under 40 with abdominal pain AND unexplained weight loss

over 50 with unexplained rectal bleeding

over 60 with a change in bowel habit or iron deficiency anaemia

investigations for colorectal cancer

COLONOSCOPY = gold standard

radiological imaging

- CT colonography

- barium enema

- CT abdomen/pelvis

staging of colorectal cancer

Duke's staging A-D

- A = confined to mucosa and part of muscle of bowel wall

- B = extending through muscle of bowel wall

- C = lymph node involvement

- D = metastatic

more advanced the disease, the worse your outlook

TNM classification of colorectal cancer

T - tumour

- TX = unable to assess size

- T1 = submucosa involvement

- T2 = muscularis propria involvement

- T3 = involvement of subserosa and serosa but not through

- T4 = spread through serosa (4a) reaching other tissues or organs (4b)

N - nodes

- NX = can't assess

- N0 = no nodal spread

- N1 = 1-3 nodes

- N2 = 3 or more nodes

M - metastasis

- M0 = no

- M1 = yes

treatment/management of colorectal cancer

colectomy

chemotherapy

radiotherapy (rectal cancer only)

surgical resection (very early lesions)

palliative care

complications of surgery in colorectal cancer

bleeding

infection

pain

damage to nerves, vessels, bladder, ureters or bowel

post op ileus

anaesthetic risk

laparoscopic surgery converted to open surgery

leakage or failure of anastomosis

requirement for stoma

failure to remove tumour

DVT

PE

incisional hernia

intra-abdominal adhesions

screening modalities for colorectal cancer

faecal occult blood test - colonoscopy if +ve

FIT

flexible sigmoidoscopy

colonoscopy

CT colonography

normal function of colon

water and electrolyte absorption

production and absorption of vitamins K and B

storage of faeces (Rectum)

hosts gut microbiota - role in immune function and diseases

arterial supply of colon

SMA - right colic, middle colic and ileocolic arteries.

IMA - left colic, sigmoid colic arteries

Marginal artery of Drummond.

innervation of colon

T10-L1

complications of a stoma

bleeding

infection

anastomotic leak

stomach problems - ischaemia, prolapse, hernia, high output

possible impaired fertility

post op management of colorectal cancer

adjuvant chemo

- complications may delay this

surveillance CT, colonoscopy

bowel obstruction cardinal signs

abdominal pain

vomiting

absolute constipation - not flatus or faeces

abdominal distension

large intestine causes of obstruction

tumour

strictures - diverticulitis

faecal impaction

pseudo-obstruction

small intestine causes of obstruction

adhesions

hernia

importance of screening

prevention method to detect early cancers in the general population, high risk groups AND those that are symptomatic - rule out test for significant bowel disease, avoiding unnecessary colonoscopy

MAP

autosomal recessive, caused by pathogenic variants in the MUTYH base-exicsion repair gene

colorectal cancer mostly right sided and synchronous

-high risk of cancer at later age (60)

-annual colorectal surveillance commencing 18-20 years

what do patients with colorectal cancer complain of the most

-Rectal bleeding – anorectal pain, colour, mixed in stool 

-Change in bowel habits (diarrhoea, constipation) 

-Fatigue 

-Abdominal pain - colicky 

-Weight loss 

-Tenesmus 

-Vomiting 

why is MRI important in rectal cancer

could dictate if neoadjuvant chemotherapy, radiotherapy or both required followed by surgery

when is colon cancer almost always straight to surgery?

if no metastatic disease & patient fit