The first description of a cancer of the colon complicating "regional enteritis" was described in 1948 . After this, published works abounded with reports of colorectal cancer in series of patients with Crohn's disease . In a recent population-based study , Bernstein et al. determined the incidence of cancer by linking records from the IBD and non-IBD cohort with the Comprehensive Cancer Care Manitoba Registry. IBD patients were matched 1:10 to randomly selected members of the population without IBD based on year, age gender and postal area of residence. There was an increased risk of colon carcinoma for both Crohn's disease patients [2.64: 95% confidence interval (95% CI), 1.69-4.12) and UC patients (2.75; 95% CI, 1.91-3.97]. There was an increased IRR of rectal carcinoma only among patients with UC (1.90; 95% CI, 1.05-3.43) and an increased IRR of carcinoma of the small intestine only in Crohn's disease patients (17.4; 95% CI, 4.16-72.9). An increased IRR of extraintestinal tumours was observed only for the liver and biliary tract in both Crohn's disease patients (5.22; 95% CI, 1.05-14.9) and UC patients (3,96; 95% CI, 1.05-14.9). Gillen et al.  concluded that when cases of ulcerative and Crohn's colitis of similar anatomic extent are followed for similar durations, the two diseases may ultimately prove to have similar increases in risk for colorectal cancer . In fact, they compared the cancer risk in two hospital-referred but identically selected cohorts of patients with extensive UC and equally extensive Crohn's disease of the colon. As in the classic 1973 paper by Weedon et al. , the overall risk of colorectal cancer was increased nearly 20-fold over the general population. Moreover, both relative risks and absolute 20-year cumulative incidences of cancer were virtually identical in the ulcerative and Crohn's colitis cohorts. This study, therefore, conclusively establishes the previously reported [85-87] but still underappreciated similarity between cancer risks in these two diseases.
Friedman et al.  in 2001 concluded that colonoscopy surveillance should be strongly considered in chronic extensive Crohn's colitis. In fact, they reported on 259 patients with chronic Crohn's colitis who underwent screening and subsequent surveillance colonoscopy and biopsy since 1980. Biopsies were performed at 10-cm intervals and from strictures and polypoid masses. A total of 663 examinations were performed on 259 patients. Median interval between examinations was 24 months. The screening and surveillance programme detected dysplasia or cancer in 16%. A finding of definite dysplasia or cancer was associated with age >45 years and increased symptoms. By life table analysis, the probability of detecting dysplasia or cancer after a negative screening colonoscopy was 22% by the fourth surveillance examination. It is interesting from a clinical point of view that the pediatric colonoscope helped increase the yield of neoplasia by 19%. Despite this report, Mpofu et al.  concluded a review indicating that there is no clear evidence that surveillance colonoscopy prolongs survival in patients with IBD with extensive colitis.
There is evidence that cancers tend to be detected at an earlier stage in patients who are undergoing surveillance, and these patients have a correspondingly better prognosis but lead-time bias could contribute substantially to this apparent benefit. There is indirect evidence that surveillance is likely to be effective at reducing the risk of death from IBD-associated col-orectal cancer and indirect evidence that it is acceptably cost effective. Therefore, the follow-up of colonic Crohn's disease must be similar to the follow-up of ulcerative colitis. Itzkowitz et al. suggested , awaiting more data about Crohn's and colorectal cancer, that it seems prudent to follow a UC-based surveillance strategy for patients with at least 8 years of Crohn's colitis involving at least one third of the colon. The suggested surveillance strategy is reported in Fig. 1 with the performance reported in Table 2 indicated by these authors. Information on family history of colorectal cancer may be a simple way to identify individuals with extensive colonic Crohn's disease at more and more elevated risk of developing colorectal cancer , especially with a first-degree diagnosed with colorectal cancer before 50 years of age.
Cases of colorectal cancer in Crohn's disease are in reality few, less than in UC, because many patients with extensive Crohn's colitis have early surgical resection, eliminating the risk of cancer . An increased number of small intestinal carcinoma in patients affected by Crohn's disease has been reported although the strength of this association (age, length of disease, characteristics and distribution) still has to be elucidated. Relative risk is estimated between six and 50 times by different authors, but small intestinal cancer is very rare, and this relative risk does not justify endoscopic surveillance. Longstanding disease, previous intestinal exclusion surgery and enterocutaneous or other types of fistulae should probably be considered for the development of cancer  for eventual clinical suspicion but not for scheduled endoscopic surveillance. Small intestinal cancer in Crohn's disease usually arises in distal ileum , and therefore it seems reasonable to attempt to extend surveillance colonoscopy to this
Fig. 1. Suggested surveillance strategy. See "Recommended Surveillance Strategy" section in text for explanation
Table 2. Suggested performance of surveillance colonoscopy
- Obtain four biopsy specimens of flat mucosa every 10 cm (consider sampling every 5 cm in the rectosigmoid)
- Place each quadruplicate set in a separate specimen jar (as opposed to pooling biopsy specimens from several colonic segments)
- Sample suspicious lesions or polyps
- Make sure to biopsy flat mucosa around the base of any suspicious polyp and submit specimen in a separate container
- Consider suppressing symptoms of active inflammation with medical therapy prior to surveillance colonoscopy
- In Crohn's colitis, strictures may require using a thinner calibre colonoscope
- Consider brush cytology or barium enema to evaluate impassible strictures bowel tract, dilating and biopsying stenosis, if possible.
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