Colorectal Cancer Flashcards
How common is colorectal cancer
3 rd most common cancer in the uk
What are type of cancer is colorectal cancers
adenocarcinomas
Rarer forms are lymphoma, carcinoid and sarcoma
How do colorectal cancers develop
originate from epithetlial cells in the lining of the colon and rectum
Progress from normal mucosa to a small adenoma (colorectal polyps) to invasive adenocarcinoma
known as the adenoma-carcinoma sequence
How many adenomas progress to adenocarcinomas
10%
Which genetic mutations predispose patients to colorectal cancer
Adenomatous polyposis coli (APC) gene - tumour suppressor gene, mutation and inactivation results in growth of adenomatous tissue
Hereditary nonpolyposis colorectal cancer (HNPCC) - mutations to DNA mismatch repair genes leading to defects in DNA repair
What are the risk factors for colorectal cancer
75% of cases are sporadic with no specific risk factors the other 25%, potential risk factors could include - age >60years - Family hx - low fibre diet - IBD - Smoking - high alcohol intake - high processed meat intake
What are the clinical features of colorectal cancer
Abdominal pain Iron deficiency anaemia change in bowel habit rectal bleeding Weight loss - more associated with mets
Right sided cancers - abdominal pain, occult bleeding, iron deficiency anaemia, mass in RIF
Left sided cancer - change in bowel habit, abdominal pain, tenesmus, mass in iliac fossa, mass on PR
What would be the differentials for colorectal cancer
IBD - onset is in younger patients and typically presents with other systemic features like ulcers and diarrhoea containing blood and mucus
Haemorrhoids - bright red blood covering the surface of the stool and on wiping, rarely presents with pain, altered bowel habits or weight loss
Diverticulitis - can present with blood in stool and change in bowel habit however unlikely to have systemic effects
How is colorectal cancer screened for
Screened every 2years in men and women aged 60-75 years old
Done using faecal occult blood home testing kits, 3 separate stool samples are needed for analysis
If any of the samples are positive then patients are offered an appointment with a specialist nurse and a colonoscopy is done
How would you investigate a patient with suspected colon cancer
bedside obs first Bloods - FBC --> may show microcytic anaemia, particularly if right sided - U+Es - LFTs - CRP - Clotting
Carcinoembryonic Antigen (CEA) should not be used as a diagnostic test, poor sensitivity and specificity. Can be used to monitor disease progression
Imaging - gold standard = colonoscopy if not suitable for colonoscopy then flexi sig or Ct colography (not as sensitive) Alternative imaging modalities - CT angiography - IV angiography
What further investigations are used
CT chest,abdo, pelvis for staging and to look for distant mets and local invasion
MRI rectum - for rectal cancers only to assess the depth of invasion
Endo-anal ultrasound - to establish suitability for trans-anal resection
How is colorectal cancer staged
Dukes staging A - confined beneath muscularis mucosa B - extension through muscularis mucosa C - involvement of regional lymph nodes D - distant metastases
How is colorectal cancer managed
All patients should be discussed in a MDT meeting
Surgery is the mainstay of treatment for localised malignancy in the bowel
Chemo - mainly used for patients with metastatic disease
Radiotherapy - given in rectal cancers, rarely given in colon cancer due to risk of damage to small bowel - most often neo-adjuvant (before main treatment)
Palliative care
What is the surgical approach for caecal or ascending colon tumours
Right hemicolectomy
the ileocolic, right colic and right branch of the middle colic vessels (branches of SMA) are divided and removed
Extended right hemicolectomy is used for transverse colon cancers
When is a left hemicolectomy used
Descending colon cancers
Left branch of the middle colic vessels - SMA
The inferior mesenteric vein and left colic vessels - IMA/IMV
