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Cancer Risk in IBD

What is the risk of developing colon cancer in ulcerative colitis?


It is accepted that there is an increased risk of colon cancer with ulcerative colitis IF

  • It has been active for at least 10 years and the disease involves at least half of the colon.
  • However the degree of risk is difficult to estimate.
    • The main underlying cause is "chronic" inflammation. If the disease has settled then the risk is significantly lower.
    • A family history of colon cancer increases the risk.
  • From point of view of most practising gastroenterologists today it seems exceptionally rare to have a death from colon cancer that has arisen in a patient with ulcerative colitis.
  • There are widely differing reported risks from different countries.
    • In fact, two studies, one from Denmark and one from Israel have suggested that the rate of colorectal cancer for their clinic population was no different from the general population.  Unfortunately no data are available from New Zealand.
  • The degree of risk of colorectal cancer in ulcerative colitis may be decreasing over recent decades.
    • The reasons for this observation are unclear.
    • There is good evidence that maintenance treatment with 5-ASA compounds(that is Salazopyrin, Pentasa, Asacol, Dipentum) decreases the risk of colorectal cancer.
    • Increasing use of these medications may be an explanation for decreasing rates of colon cancer.
  • Regular clinic follow-up is also associated with decreased risk.


Screening colonoscopies.

  • Many studies have shown that regular colonoscopies are effective in detecting early colon cancers.
    • The main aim is to identify changes that predict an increased risk of colorectal cancer. These pre-cancerous changes are called dysplasia and may classified as mild or severe.
  • It is difficult to run a comprehensive screening program.
    • All studies have shown that more cancers are diagnosed outside of the screening programme.
    • Less than half of patients stay in a regular surveillance programme (for whatever reasons).
  • The frequency of screening procedures required to reduce the risk of colorectal cancer is debated.
    • Shorter intervals between procedures may be better but public funding of health requires strong evidence for cost-effectiveness.
    • A reasonable compromise is 3-yearly colonoscopy after 10 years of ulcerative colitis.
    • The well motivated person with ulcerative colitis should have surveillance colonoscopy at an interval of 2 yearly after 8 years of the diagnosis.
  • When is an operation (colectomy) required?
    • See ulcerative colitis section for details on surgery.
    • If there is any dysplasia (changes on microscopic examination of biopsies) then a repeat colonoscopy in 6 months is required.
    • If the changes persist, then an operation is required to prevent the formation of cancer of the colon.
    • When the colon is removed there is no longer any risk.
    • Usually the risk of cancer is only a small part of decision to proceed to surgery. The main issue is usually the current quality of life and what improvement could be expected after surgery.
  • There may be an increased risk of colon cancer with colonic Crohn's disease.
    • This risk is small (many studies have not shown any difference from the risk for the general population).
    • Regular surveillance by colonoscopy has not been the policy for most gastroenterology departments but should be considered on an individual basis.





What are the main messages?

  • Regular clinic attendance and discussion of individual risks with your physician is sensible.
  • The use of maintenance long-term 5-ASA drugs does appear to have some protective effects (50% decrease in risk).
  • Azathioprine treatment does not increase the risk - may even decrease the risk
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