Sessile Serrated Polyps with Synchronous Conventional Adenomas Increase Risk of Future Advanced Neoplasia

Background: Surveillance colonoscopy guidelines following adenomas or sessile serrated adenomas/polyps (SSPs) are based on pathology features known to be associated with risk of future colorectal cancer. A synchronous conventional adenoma may increase the malignant potential of SSP, but current guidelines do not address this combination of pathologies. Aims: The aim was to assess the risk of advanced neoplasia after SSP with or without synchronous adenoma compared to that following a conventional adenoma. Methods: An audit was conducted on colonoscopies performed between 2000 and 2014 as part of a surveillance program. Index colonoscopy findings were classified as: low-risk SSP and high-risk SSP (size ≥ 10 mm or with cytological dysplasia) with and without synchronous adenoma; high-risk adenoma and low-risk adenoma. Risk of advanced neoplasia was determined at subsequent surveillance colonoscopies. Results: In total, 2157 patients had adenoma or SSP found at index colonoscopy—low-risk adenoma (40%), high-risk adenoma (54%) and SSP (4%). Synchronous adenomas were seen with 47% of SSP. The median follow-up was 50.3 months (interquartile range 28.1–79.3). Compared to an index finding of low-risk adenoma, index findings of high-risk adenoma, as well as SSP with synchronous adenoma, were independent predictors of future advanced neoplasia (high-risk adenoma: hazard ratio (HR) = 2.04 (95% CI 1.70–2.45); high-risk SSP + adenoma HR = 3.20 (95% CI 1.31–7.82); low-risk SSP + adenoma: HR = 2.20 (95% CI 1.03–4.68)). Conclusions: Synchronous adenoma increases the risk of advanced neoplasia for SSP equivalent to that seen following high-risk adenoma. Guidelines for surveillance should take into account concurrent pathologies with SSP.