Progression of low-grade dysplasia to advanced neoplasia based on the location and morphology of dysplasia in ulcerative colitis patients with extensive colitis under colonoscopic surveillance

Background: The management of low-grade dysplasia (LGD) in ulcerative colitis (UC) patients remains unclear.

Aim: The aim of our study was to study the risk of progression of LGD to advanced neoplasia (AN), defined as high-grade dysplasia (HGD) or colorectal cancer (CRC) for UC patients undergoing surveillance based on location and morphology of LGD.

Methods: 997 UC patients underwent 3152 surveillance colonoscopies from 1998 to 2011. Kaplan-Meier estimates and incidence rates calculated.

Results: Of the 102 patients with LGD (65 raised and 37 flat), 5 (4.9%) patients progressed to AN (3 HGD and 2 CRC) after a median follow-up of 36 months (interquartile range 18-71 months). Initial location of dysplasia was in the proximal colon in 47, distal colon in 55 patients. Four of the 5 (80%) patients with AN had initial dysplasia in the distal colon. Distal colonic LGD had an incidence rate for AN of 2.1 cases per 100 person years at risk, while proximal LGD had an incidence of 0.5 cases per 100 person years. Flat LGD in the distal colon was more likely to progress to AN [hazard ratio=3.6; 95% confidence interval, CI (1.3-10.6)]. Twenty of the 102 patients (15 flat and 5 raised) underwent colectomy: 2 (10%) had evidence of AN in colectomy (1 HGD and 1 CRC), 9 had LGD and remaining 9 did not have dysplasia.

Conclusions: The frequency of progression of LGD to AN is low. Flat dysplasia located in the distal colon is associated with a greater risk of progression to AN.