Progression of low-grade dysplasia in ulcerative colitis: Effect of colonic location

Background: Emerging evidence suggests that the biology of sporadic colorectal neoplasia may differ between the proximal and distal colon. Whether such a difference exists in colitis-associated colorectal neoplasia is unknown. Objective: To compare the rate of progression to advanced neoplasia (AN) between proximal and distal dysplasia in patients with ulcerative colitis (UC). Design: Retrospective cohort study. Setting: Tertiary medical center. Patients: From an institutional database of more than 700 patients with UC who underwent 2 or more surveillance colonoscopies between 1994 and 2006, we identified patients with extensive UC and low-grade dysplasia (LGD). Neoplasia proximal to the splenic flexure was considered proximal. Main Outcome Measurement: Progression to AN, defined as high-grade dysplasia (HGD) or colorectal cancer (CRC). Results: Among 121 patients with LGD, all 7 who progressed to CRC and 6 of 8 who progressed to HGD had distal LGD initially. Subjects with distal LGD had a significantly shorter time to progression than those with proximal LGD (P =.019); 5-year AN-free survivals for distal and proximal LGD were 75 ± 7% and 95 ± 3%, respectively (hazard ratio [HR] 5.0; 95% CI, 1.1-22.0). Additionally, flat LGD was significantly more likely to progress than raised LGD on univariate testing (HR 3.6; 95% CI, 1.3-10.1). Neither morphology nor sidedness remained significant in multivariable testing, although there was little change in the HRs (HR 2.4; 95% CI, 0.8-7.1 for morphology; HR 3.5; 95% CI, 0.7-16.8 for sidedness) in proportional hazards modeling. Limitations: Nonrandomized, retrospective trial and low incidence of AN. Conclusions: In patients with long-standing, extensive UC, distal LGD is more common and progresses more rapidly to AN than proximal LGD.