What should be the protocol to manage low grade dysplasia in IBD?
The significance of low grade dysplasia (LGD) in flat mucosa is controversial. Data from tertiary referral centres have generally shown it is associated with progression to high grade dysplasia or cancer. Of 47 patients who were diagnosed with LGD at St Mark’s Hospital, 20% eventually developed CRC and 39% developed either HGD or cancer. At Mount Sinai Hospital, the rate of progression to higher grades of neoplasia was 53% at five years. These results contrast with other data which show progression from LGD to advanced neoplasia is slow, and is not invariable. A meta-analysis of 20 surveillance studies involving 508 cases of low grade dysplasia in flat mucosa or dysplastic mass lesions found the cancer incidence to be 14 per 1000 person years duration, and the incidence of any advanced lesion was 30 per 1000 person years duration. The positive predictive value of LGD for concurrent cancer was 25% and for progression to cancer was 8%.
Because of the uncertainty about the predictive value of LGD in flat mucosa, it is recommended that surgery be considered if it is multifocal. However, patients with LGD in flat mucosa who wish to avoid an operation require repeat colonoscopy at three to six months, preferably with chromoendoscopy, and thereafter at yearly intervals. A finding of unifocal low grade dysplasia in flat mucosa is less likely to be associated with imminent cancer, and follow-up colonoscopy is reasonable within six months in these cases.
Evidence summary and recommendations
|The predictive value of low grade dysplasia in flat mucosa for future cancer is controversial, but probably higher if it is located in multiple synchronous sites.||III-2||, , , , , |
|Multifocal low grade dysplasia is associated with a sufficiently high risk of future cancer that colectomy is usually recommended. Patients who elect to avoid surgery require follow up surveillance at three months, preferably with chromoendoscopy, and if this examination is normal, annually.||C|
|Unifocal low grade dysplasia may be followed by ongoing surveillance at six months, and if this examination is normal, annually.||C|
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