Colorectal Cancer Flashcards
Colorectal cancers most common type
- Originate from epithelial cells lining colon
- Adenocarcinoma most common
How do colorectal cancers develop?
- Progression or normal mucosa to colonic adenoma (colorectal polyps) and then to invasive adenocarcinoma
- Adenomas can be present for 10yrs or more before becoming malignant - 10% progress to adenocarcinoma
Genetic mutations implicated in pre-disposing to colorectal cancer
- Adenomatous polyposis coli (APC) - APC is a tumour supressor gene which is mutated –> growth of adenomatous tissue eg familial ademomatous polyposis (FAP)
- Hereditary nonpolyposis colorectal cancer (HNPCC) - DNA mismatch repair gene, defects in DNA repair –> Lynch syndrome
Adenoma carcinoma sequence
Normal epithelium –> abnormal epithelium –> small adeoma –> large adenoma –> colonic carcinoma
RF for colorectal cancer
- Sporadic usually - no specific RF
- Increasing age
- Male
- FH
- IBD
- Low fibre diet
- High processed meat intake
- Smoking
- Excess alcohol intake
Symptoms of colorectal cancer
- Change in bowel habit
- Rectal bleeding
- Weight loss - usually only present if metastasised (unlike upper GI)
- Abdominal pain
- Symptoms of iron deficiency anaemia
Right sided vs left sided colon cancer symptoms
Right sided:
* Abdominal pain
* Iron deficiency anaemia
* Palpable mass RIF
* Often presents late
Left sided:
* Rectal bleeding
* Change in bowel habit
* Tenesmus
* Palpable mass in LIF or on PR
NICE criteria for 2WW referral for suspected bowel cancer
- 40 years or older with unexplained weight loss and abdominal pain
- 50 years and older with unexplained rectal bleeding
- 60 years and older with iron deficiency anaemia or change in bowel habit
- Positive occult blood screening test
Colorectal cancer screening
- Faecal immunochemistry test
- Every 2 years to men and women aged 60-75
- Uses antibodies against human Hb to detect blood in faeces
- If +ve - appointment with specialist nurse and colonoscopy
Bedside and bloods for ?colorectal cancer
- FBC - microcytic anaemia?
- LFTs
- Clotting
- Carcinoembryonic antigen (CEA) tumour marker - monitor disease progression pre and post treatment but NOT to diagnose (poor specificity and sensitivity)
Elevated baseline CEA = worse prognosis
Imaging for colorectal cancer
- Colonoscopy + biopsy = gold standard
- If unsuitable eg frailty, co-morbids CT colonography can be done
Once diagnosis made, other investigations for staging colorectal cancer
- CT scan - chest abdomen and pelvis - look for mets and local invasion
- MRI rectum - for rectal cancers only, assess depth of invasion and need for pre-op chemo
- Endo-anal USS - early rectal cancer T1 or T2, check for trans-anal resection suitability
What happens to biopsy samples?
- TNM
- Histological subtyping
- Grading
- Assess for lymphatic, perineural (nerve invasion) and venous invasion
- Tumour markers also assessed - identify Lynch syndrome and optimise chemo regimes
Additional staging for colorectal cancer (other than TNM)
- Dukes - not used as often now
- A-D
- A is confined to muscularis propria
- B - extends through MP
- C - involved regional lymph nodes
- D - distant mets
General management colorectal cancer
- Discuss MDT
- ONLY curative option is surgery
- Chemotherapy and radiotherapy have important role as adjuvant and neoadjuvant therapy and palliation
Surgical plan in general for colorectal cancer
- Regional colectomy usually with good margins and removal of lymphatic drainage
- Then either primary anastomosis or formation of stoma
Typical surgeries for colorectal cancer
- Right hemicolectomy or extended right hemicolectomy
- Left hemicolectomy
- Sigmoidcolectomy
- Anterior resection
- Abdominoperineal resection
- Hartmanns
Right hemicolectomy or extended right hemicolectomy
- For caecal tumours or ascending colon tumours
- Extended option if involving transverse colon
- Ileocolic, right colic and middle colic vessels divided and removed with mesenteries
Left hemicolectomy
- For descending colon tumours
- Left branch of middle colic vessels, inferior mesenteric vein and left colic vessels divided and removed with mesenteries
Sigmoidcolectomy
- For sigmoid colon tumours
- IMA fully dissected out with the tumout to ensure adequate margins
Anterior resection
- For high rectal tumours - typically if >5cm from anus
- Remove rectum and sigmoid colon
- Leaves rectal sphincter intact if anastomosis performed
- Defunctioning loop ileostomy done to protect anastomsis and reduce risk of leak - reverse in 4-6 months
Abdominoperineal resection
- For low rectal tumours - within 5cm of anus
- Excise distal colon, rectum and anal sphincters
- = permanent colostomy
Hartmanns procedure
- Emergency bowel surgery
- Eg bowel obstruction or perforation
- Complete resection of recto-sigmoid colon with formation of end colostomy and closure of rectal stump
How can colorectal cancer presenting as bowel obstruction be managed?
- Decompressing colostomy OR endoscopic stenting
- Then staging and patient status can be optimised
When is chemotherapy used for colorectal cancer?
- Advanced disease
- Metastatic
- Is tailored with patient specific and disease specific predictive markers
Examples of chemotherapy regime for colorectal cancer
- FOLFOX
- Folinic acid
- Fluourouracil
- Oxaliplatin
Also newer biologic agents and immunotherapy
When is radiotherapy used?
- Rectal cancer - rarely given in colon due to risk of damaging small bowel
- Neo-adjuvant and can be alongside chemotherapy
- Useful if threatened circumferential resection - if cancer will be within 1mm of resected margins
- So have pre-op long course chemoradiotherapy to shrink so increase chance of complete resection and cure
- Then surgery 8-10 weeks after
What can sometimes happen to rectal cancer with chemo-radiotherapy?
- Complete response
- Rectal preserving approach sometimes and watch and wait with close surveillance
Palliative care for colorectal cancer
- Very advanced
- Focus on reducing cancer growth and ensuring symptom control
