Introduction: Patients with serrated lesions (SL) (sessile serrated lesion (SSL) or traditional serrated adenoma (TSA)) or high-grade dysplastic adenomas (HGD) are at risk to develop advanced colorectal adenomas (AA) or colorectal cancer (CRC). The study aim was to compare the incidence of total metachronous advanced neoplasia (TMAN) in surveillance colonoscopies of patients diagnosed with SL < 10 mm, SL ≥10 mm or HGD at index colonoscopy.
Methods: A retrospective cohort study was conducted. Through pathology database search, we identified 1529 patients with HGD and 2428 patients with SL diagnosed between 2010 and 2019 at the University of Montreal Hospital Center. We excluded patients under 45 or over 75 years of age, with inflammatory bowel disease, hereditary CRC syndromes, previous or synchronous CRC, first surveillance < 12 months after complete index, or concomitant SL and HGD at index. Patient files were reviewed for demographic data and findings at index and follow-up colonoscopies. Follow-up was continued until the outcome of interest or the last colonoscopy within 10 years. The primary outcome was TMAN (defined as advanced neoplasia (AN), which combines AA and CRC, or advanced serrated lesion (ASL), defined as SSL ≥10 mm or with dysplasia, TSA or hyperplastic polyp (HP) ≥10 mm). We performed univariate and multivariate Cox regressions.
Results: A total of 585 patients were eligible (55% male, mean age 63 years). The mean duration of follow-up was 3.67 years (range 0.94 – 9.88 years). There were 226 patients in the SL < 10 mm group (216 SSL and 10 TSA), 204 patients in the SL ≥10 mm group (198 SSL and 6 TSA) and 155 patients in the HGD group. Compared to SL < 10 mm (reference group), SL ≥10 mm resulted in a higher rate of TMAN (HR=2.08 (1.38-3.15)), a similar rate of AN (HR=1.45 (0.81-2.77)), and a higher rate of ASL (HR=2.53 (1.50-4.25)) after adjusting for age, sex, family history of CRC, proximal location of HGD or SL, tubulovillous or villous adenomas (TVA/VA), adenomas ≥10 mm and ≥3 adenomas. Compared to SL < 10 mm, HGD resulted in a similar rate of TMAN (HR=0.87 (0.62-1.20)) and AN (HR=1.08 (0.74- 1.57)), and a lower rate of ASL (HR=0.40 (0.19-0.85)), after adjusting for the same covariates.
Discussion: Patients with a SL ≥10 mm at index colonoscopy have the highest risk of developing TMAN compared to patients with HGD and to patients with SL < 10 mm. This risk should be considered when planning surveillance intervals for patients with SL ≥10 mm.
