Malignant growths within the intestines are common in the West and are curable if detected early.
The small intestine is where the bulk of digestion takes place; despite its great activity it is unusual to develop cancer here. Cancer is far more common in the large bowel, even though it is a less energetic environment. Most growths arise in the final part of the large bowel, called the descending colon, the rectum and just inside the anus itself.
Bowel cancer, the second most common cancer in the United Kingdom, is rare in Africa and Asia, which suggests that environmental factors are involved. Possibly the Western low-fibre diet means that faeces remain in the large intestine for longer so that any cancer-producing agents in the diet have longer to influence the cells of the bowel wall.
There is a genetic tendency to bowel cancer: people with a close relative who has it have a two to four times increased risk themselves. People with ulcerative colitis (see Inflammatory bowel disease) have as much as a 40 times increased chance of bowel cancer once they have had colitis for more than 15 years.
The disease is most common after the age of 60, and is rare below 40 except in the high-risk groups above.
Change of bowel habit is the prime symptom to be aware of, whether it is towards diarrhoea or towards constipation. Temporary changes of this sort arc extremely common;
changes lasting more than a couple of weeks need investigating. Bleeding from the bowel is another ‘must investigate’ symptom, even though there are plenty of benign causes.
Anaemia in an otherwise healthy adult with a good diet is a possible indication of internal bleeding from a silent growth and investigation would be recommended. Other symptoms may include weight loss and abdominal pains, although these are features of more advanced disease.
A rectal examination picks up about one-third of all bowel tumours. Other bowel investigations include checking the stools for traces of blood, sigmoidoscopy, colonoscopy and barium enema.
If caught early, when the cancer is confined to the surface layer of the bowel, bowel cancer is virtually curable – there is a better than 95% five-year survival. Treatment involves an abdominal operation to cut out the tumour with part of the bowel and to rejoin the healthy bowel. Modern surgical techniques mean that it is now uncommon to need a colostomy, other than as a temporary measure, except for tumours that are sited very close to the anus.
Once the cancer has spread deeper inside the wall of the bowel or into the surrounding tissue, the chances of a cure are less, there being a 30-65% five-year survival. Radiotherapy and chemotherapy are slowly improving these figures, however.
Is screening worthwhile?
Trials are now testing the value of regular screening of people after the age of 50, for example by testing a stool sample for blood or by using sigmoidoscopy every five to ten years. People at high risk of bowel cancer should have regular colonoscopy of their bowel in order to detect early disease – every three years at least.
What happens with untreated cancer?
See Stomach Cancer