The cause of cancer of the colon is unknown despite extensive and continuing
research. It is well documented that there is an increased risk of developing
cancer in ulcerative colitis when compared to the general population,
although it is now thought that the risk is much lower than previously
Most patients never develop cancer, but its early detection in patients
at increased risk can lead to prompt, curative treatment. The increased
risk should therefore not cause you great concern as after having ulcerative
colitis for around ten years, you will be offered regular screening.
Patients with proctitis only need not undergo screening.
The risk of developing cancer is related to two main factors:
1. The duration of inflammation, (i.e. the length of time since it was
2. The extent of inflammation (the risk is higher with total colitis).
There appears to be some evidence that it occurs more frequently in
chronically active disease than it does in previously active or intermittent
disease. Patients whose colitis is under good control with drugs such
as Salazopyrine and Mesalazine are believed to be at reduced risk.
Studies have shown that the chance of developing cancer of the colon
rises steadily in all patients with the length of time the disease has
10 years of total disease (pancolitis) the risk increases to around
i.e. out of 100 patients with extensive disease, approximately
4-5 patients may develop cancer.
20 years the risk is around 7 - 8%, i.e. out of 100 patients with extensive
disease approximately 7 - 8 patients may develop cancer.
All figures are independent of age of onset of the disease. Some studies
have reported figures for risk which are higher or lower than those above.
Extent of Disease
75 - 80% of patients with ulcerative colitis who develop cancer of the
colon have a history of pancolitis. There is some evidence that a history
of left-sided colitis can predispose to cancer but usually this occurs
around ten years later than with pancolitis. The risk of cancer in proctitis
is no greater than that in the general population.
Where does it occur?
The most common site for cancer of the colon in ulcerative colitis to
develop is the rectosigmoid area (50%). The second most common is the
What are the signs and symptoms?
These may be variable according to the site and extent of the cancer
but generally include:
change in bowel habit (with or without blood).
• Abdominal pain and flatulence (wind).
• Anorexia (poor appetite).
Late symptoms may include:
• Fatigue (probably due to anaemia)
• General deterioration in health
N.B. After 10 years of colitis, therefore, such symptoms should be taken
seriously and discussed with your doctor.
How can it be detected?
It is generally recommended that a colonoscopy be carried out at 7 -
10 years following the first signs of disease. If extensive disease is
present this should then be performed on a regular basis. An average
of 2 - 3 biopsies should be taken per site at approximately 8 sites.
Dysplasia is an alteration in the size, shape and organisation of mature
cells seen under the microscope. Evidence of dysplasia is generally viewed
as a sign of the possibility of future cancer development. Some gastroenterologists
believe that it may mean that early cancer is already present.
Dysplasia may be classified as:
• low grade
Individual pathologists' views on the grade of dysplasia vary considerably
and therefore several opinions or an opinion from a pathologist with
expertise in looking at colonic dysplasia may be taken, especially when
a decision on colectomy is to be made.
Colonoscopic biopsies showing dysplasia of any grade increase the risk
of having a cancer or of developing one in the future. You can generally
be reassured that no dysplasia means no cancer.
A positive biopsy for dysplasia is not always diagnostic of cancer but
high grade dysplasia is usually considered sufficient evidence to justify
removal of the colon.
What happens if signs of cancer are found?
Surgery is usually indicated if the following signs are present:
obvious cancer is found on colonoscopy.
presence of dysplasia of any grade is associated with another lesion
is found on repeated colonoscopy, or multiple areas of dysplasia are
present on any single examination.
grade dysplasia on a single examination
What surgery is performed?
There are 2 choices of surgery:
1. Total colectomy and formation of an ileostomy. The colon is removed,
therefore providing a cure of the disease and eliminating any further
risk of colonic cancer.
2. Formation of an ileo anal pouch. The rectum is preserved following
removal of the mucosal layer. A pouch is formed from loops of small bowel
(ileum) and joined to the rectal muscle. As the anal sphincter muscles
remain intact, normal bowel control is present. It may be carried out
in a single operation or as a two-stage procedure with the formation
of a temporary ileostomy allowing the operation site to heal without
the continued presence of bowel motions to hinder it.
As ulcerative colitis is a disease of the mucosa, the remaining rectum
should carry no more risk of cancer development than would be expected
in the general population. However, inflammation may develop in the new
There are some gastroenterologists who advise prophylactic colectomy
(removal of the bowel without presence of dysplasia). A mutual decision
can be made between doctor and patient in which surgery is considered
preferable to years of uncontrolled colitis, disruption of social and
working life and possible repeated hospital admissions either for treatment
of severe colitis or for regular surveillance colonoscopy.
New developments are occurring continually in the effort to detect cancer
early. These include:
Some centres are able to look at genetic material (DNA) from colonic
biopsies but this method is in the very early stages of evaluation in
its effectiveness of determining the possible development of cancer.
Special immunostaining of biopsies may indicate the presence of early
Examining the blood and stools of patients with long-standing colitis
may show evidence of chemicals which reliably predict the presence of
Research is being carried out into the value of these tests as a method
of screening alone or in combination with colonoscopy.