Colorectal carcinoma

 

Pathology

Two thirds in carcinomas occur in the rectosigmoid area

Tumours is usually polypoid mass with ulceration

Spread is initially by direct invasion of the bowel wall

Next it invades the lymphatics and blood vessels with early spread to the liver

Widespread metastases eg. lung can occur

 

Adenoma to carcinoma

Polyps may develop in the colon which may become malignant

Most cases are a progression from normal mucosa, through adenoma to invasive cancer

Familiar adenomatous polyposis - 100% chance of malignancy developing between 20 - 40 years of age

Inactivation of APC (Adenomatosis polyposis coli) tumour suppressor gene

 

Epidemiology

Adenocarcinoma is the second most common malignancy in the UK, lifetime incidence of 1 in 50

Average age on diagnosis is 60 - 65

 

Aetiology

Uncommon in traditional Africa and Asia - for environmental reasons

Positively correlated with meat and animal fat consumption

Bacterial flora is effected by diet

Certain bacteria convert bile acids to carcinogens

Fibre is a factor

Fruit and vegetables are protective

Exercise is protective

Aspirin and other NSAIDs reduce risk of adenomas and cancers

Oestrogen and progesterone HRT may be protective

Several oncogenes have been identified

Two to three times greater chance of developing bowel cancer if first order relative is affected

 

Familial adenomatous polyposis 1%

Familial 10 - 30%

Sporadic about 70%

 

Clinical features

Alteration in bowel habits

Bleeding

Iron deficiency anaemia

Possible pain

Intestinal obstruction

Mass may be palpable

Weight loss

Liver metastases cause hepatomegaly

 

Investigations

Enema followed by direct observation - colonoscopy - biopsy

Barium enema

Ultrasound

 

Screening

Universal FOB screening reduced mortality by 33%

Some recommend a single flexible sigmoidoscopy at 55, especially in those with first or second degree relatives affected

 

Treatment

Resection

End to end anastomosis if possible

Colostomy

Additional chemotherapy for more advanced cases

Overall survival after 5 years is 30% but is 95% if treated when only involving the gut wall