Dr John P Wright
Updated 11 July 2011
The risk of colon cancer in patients with ulcerative colitis has apparently been falling over the last 20 years. In 1983 the risk of developing colon cancer was thought to be about 30% in patients who had had ulcerative colitis for 35 years with greater extent and younger age at onset being aggravating factors(1). A more recent estimate was given in a meta-analysis suggesting that the cumulative incidence of colon cancer was now 8% at 20 years and 18% after 30 years (2). The background risk in the matching noncolitic population would be about 20% in a lifetime. This confirmed what had been apparent to clinicians seeing many patients with inflammatory bowel disease that while the expected incidence was depressing the experience was that this high incidence was not being seen. Further confirmation of this impression was published from St Marks in London this year(3) where a prospective incidence of 2.5% after 20 years and 7.6% after 30 years of follow up was found. This lower incidence was more remarkable as the patient cohort studied was thought to be 87% tertiary referral patients. This would have been expected to increase the risk by excluding the less severe patients seen in the community.
This view is supported in a prospective population based study just published from Minnesota, USA(4) which suggests that the incidence of colon cancer in patients with ulcerative colitis or Crohn’s disease may be no higher than that of the general population. It was only in the case of small bowel tumours that Crohn’s disease patients had a 40 fold increased incidence. Many of patients in this study had been on maintenance therapy and had had regular colonoscopic surveillance. This result therefore suggests that with modern management we might be able to reduce the threat of colon cancer in our patients to the background risk. The early detection of small bowel tumours in patients with Crohn’s disease however remains a challenge.
In addition to the possible reduced incidence of colorectal cancer, the St Marks study found that the 5 year overall survival of 73.3% has higher than the generaly high 50 to 60% seen in noncolitis colon cancer in the USA and Western Europe.
This new information has profound implications. Not least in the anxiety generated in patients with inflammatory bowel disease by the previous expectations. This anxiety has been further stoked by endoscopists performing over zealous surveillance colonoscopies to detect early cancer. Less direct but perhaps equally important is the attitude of the life insurance industry to these patients where insurance is often denied.
This data is so important that it needs to be carefully assessed and will need to be confirmed before drastic action is taken. In the St Marks study patients with ulcerative colitis proximal to the splenic flexure were colonoscoped every one to two years starting 8 years after diagnosis. On average 8 biopsies were taken from around the colon at each procedure. This is in contrast to the current recommendations of once every 3 years but with more extensive mucosa sampling
While it may be tempting to believe that the risk of colon cancer complicating inflammatory bowel disease has been overstated, this would be an incorrect interpretation at present. These studies do however show that with current treatments standards of maintenance therapy including Mesalazine, immunosuppression and the anti-TNF antibodies together with regular surveillance colonoscopy patients can be re-assured that their risk of colon cancer can be largely controlled.