The influence of the surveillance time interval on the risk of advanced neoplasia after non‐advanced adenoma removal

Objectives To investigate the incidence of advanced neoplasia (colorectal cancer or advanced adenoma) at surveillance colonoscopy following removal of non‐advanced adenoma; to determine whether the time interval before surveillance colonoscopy influences the likelihood of advanced neoplasia. Design Retrospective cohort study. Setting, participants Patients enrolled in a South Australian surveillance colonoscopy program with findings of non‐advanced adenoma during 1999–2016 who subsequently underwent surveillance colonoscopy. Main outcome measures Incidence of advanced neoplasia at follow‐up surveillance colonoscopy. Results Advanced neoplasia was detected in 169 of 965 eligible surveillance colonoscopies (18%) for 904 unique patients (median age, 62.0 years; interquartile range [IQR], 54.0–69.0 years), of whom 570 were men (59.1%). The median interval between the initial and surveillance procedures was 5.2 years (IQR, 4.4–6.0 years; range, 2.0–14 years). Factors associated with increased risk of advanced neoplasia at follow‐up included age (per year: odds ratio [OR], 1.03; 95% CI, 1.01–1.05), prior history of adenoma (OR, 1.48; 95% CI, 1.01–2.15), two non‐advanced adenomas identified at baseline procedure (v one: OR, 1.74; 95% CI, 1.18–2.57), and time to surveillance colonoscopy (OR, 1.21; 95% CI, 1.08–1.37). The estimated incidence of advanced neoplasia was 19% five years after non‐advanced adenoma removal, and 30% at ten years. Conclusions Increasing the surveillance colonoscopy interval beyond five years after removal of non‐advanced adenoma increases the risk of detection of advanced neoplasia at follow‐up colonoscopy.