Colorectal cancer Flashcards
Epidemiology
3rd commonest cancer in UK
Majority >60 but can occur at any age
Much commoner in Western countries
Risk reduced by veg, garlic, milk, exercise, aspirin + NSAIDs
Screening
60-75 offered every 2y with faecal occult blood home testing (3 separate stool samples, if any + offered colonoscopy), and at 55y offered a one-off flexisig (it cannot reach all CRCs)
Risk factors (only applicable to 25%)
- Age >60
- Family history: either a known syndrome or other genetic link
- IBD esp UC
- Low fibre, high processed meat diet
- Smoking
- High alcohol intake
HNPCC (Lynch syndrome)
- Most common hereditary CRC
- Early age of presentation + higher risk of other cancers (esp endometrial)
- Proximal colonic adenomas that progress over 2-3y to cancer (quicker progression), without polyposis
- After first adenoma they need colectomy
Familial adenomatous polyposis
- Autosomal dominant gremlin mutation in the FAP gene
- Hundreds-thousands adenomas polyps throughout colon, if not treated develop CRC by age 35ish
- Also linked to duodenal, desmoid (benign) and pancreatic tumours
- APC gene also linked to other syndromes part of FAP spectrum e.g. Gardner syndrome (colon polyposis + osteomas + dental abnormalities + soft tissue tumours)
What is the histopathology?
- Usually adenocarcinoma, that progress from a normal mucosa to colonic adenomas then to invasive adenocarcinomas after many years
- Rare types - lymphoma, carcinoid, sarcoma
Presentation
- Change in bowel habit - looser/more frequent
- PR bleeding
- WL - usually only if mets or causing subacute obstruction
- Abdo pain
- Iron-def anaemia (esp right colon)
- Acutely with bowel obstruction
- Right-sided often abdomen pain, occult bleeding causing anaemia or mass in RIF
- Left-sided often more obvious with PR bleed, changed bowel habit, tenesmus, mass in LIF, mass on DRE
NICE guidelines for 2ww referrals
- 40+ with unexplained WL + abdo pain
- 50+ with unexplained PR bleeding
- 60+ with iron-deficiency anaemia/change in bowel habit
- Positive occult faecal blood test
- Rectal/abdominal mass
- Aged <50 with rectal bleeding and any one of: abdo pain, change in bowel habit, weight loss, iron-deficiency anaemia
Differentials
- IBD: usually 20-40y onset with diarrhoea blood + mucus
- Haemorrhoids: bright red blood covering stool, rare to have constitutional sx or abdo pain
- Diverticulitis: usually systemic inflammation features + changed bowel habit + blood
Staging
TNM (used to be Duke’s)
Stage I: N0, M0; tumour in submucosa (T1) or muscularis propria (T2)
Stage IIa (N0, M0) in sub-serosa (T3)
Stage IIb (N0) direct invasion to visceral peritoneum or other organ (T4)
Stage III (N1, M0) IIIa T1-2 or IIIb T3-4 [up to 3 LN]
Stage IV: any T, 4 or more LN, any distant mets
Management overview
- Surgery: only curative option. A regional colectomy with adequate margins + lymph drainage, then a primary anastomosis or stoma for bowel function. Often only treatment used
- Chemo: in metastatic
- Radio: not usually given cos of damage to bowel wall but sometimes used neo-adjuvant in rectal
- Palliative: endoluminal stenting to relieve obstruction, stoma for acute obstruction, liver met resections
Types of surgery based on location of tumour
- Caecum/ascending colon: right hemicolectomy
- Transverse colon: extended right hemicolectomy
- Descending colon: left hemicolectomy
- Sigmoid: sigmoidectomy
- High rectal: anterior resection. If >5cm away from the anus, better in rectal cancer as leaves functioning rectal sphincter, defunctioning loop ileostomy to protect anastomosis then reversed once healed
- Low rectal: abdominoperineal resection. If <5cm from anus, have to excise distal colon + rectum + anal sphincters so need permanent colostomy. Do when cannot get a 1cm clear margin of rectum below the tumour
- Emergency: Hartmann’s procedure. Complete resection of recto-sigmoid colon + end colostomy + closure of rectal stump
Gastrointestinal stromal tumours
These are rare soft tissue tumours of mesenchymal origin, anywhere in GIT but majority in stomach or SI
CF: early satiety, bloating, fatigue, fever, WL, night sweats, GI bleeding (commonest PC), sx of mass/obstruction
RF: familial syndromes, NF1
All have potential to become malignant, vary in aggressiveness, usually met to liver or in abdomen but distant mets unusual
M: localised complete resection avoiding rupture + imatinib if KIT-positive, if advanced some may still be resectable or just give imatinib
Metastasis?
Liver and lung via haematogenous spread
Investigations
- Routine bloods - may have microcytic anaemia
- CEA - for monitoring progression, NOT for diagnosis as poor S+S
- Colonoscopy + biopsy is gold standard
- Post-diagnosis: CT CAP for staging, MRI rectum if rectal to see depth of invasion + endo-anal US to assess resection suitability
