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 (UC) when compared to the general population, although it is now thought that the risk is much lower than previously believed.
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 UC 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:
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 sulfasalazine and mesalazine, which reduce inflammation are therefore believed to be at less 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 been present:
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.
75 – 80% of patients with UC 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.
The most common site for cancer of the colon in UC to develop is the rectosigmoid area (50%). The second most common is the caecum.
These may be variable according to the site and extent of the cancer but generally include:
N.B. After 10 years of colitis, therefore, such symptoms should be taken seriously and discussed with your doctor.
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:
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.
Surgery is usually indicated if the following signs are present:
There are 2 choices of surgery:
As UC 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 pouch (pouchitis).
There are some gastroenterologists who advise prophylactic colectomy (removal of the bowel without presence of dysplasia). A mutual decision can be reached between doctor and patient following discussions in which surgery may be 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: