Risk of Advanced Colorectal Neoplasia at Follow-up Colonoscopy After Synchronous Adenoma and Clinically Significant Serrated Polyp

Background & Aims
Colorectal cancer (CRC) commonly develops from pre-cancerous neoplasia through the adenoma-carcinoma and/or serrated pathways. Individuals with an adenoma or clinically significant serrated polyp (CSSP) are recommended to undergo surveillance colonoscopy to reduce risk of future CRC. However, the risk of CRC after synchronous adenoma and CSSP remains unclear. We determined the risk of advanced neoplasia (advanced pre-cancerous neoplasia and/or CRC) at follow-up colonoscopy after a synchronous adenoma and CSSP in comparison to other types of neoplasia.

Methods
A retrospective analysis was conducted on colonoscopy outcomes between 2010-2023 on patients in a South Australian CRC surveillance program. Risk of advanced neoplasia at follow-up colonoscopy was determined based on prior colonoscopy findings using competing-risk regression.

Results
A total of 8,481 colonoscopy pairs were included. Advanced neoplasia was found in 11% (973/8,481) of follow-up colonoscopies. Risk of advanced neoplasia was highest in those with advanced synchronous adenoma and CSSP (hazard ratio (HR) 4.71, 95% confidence interval (CI) 3.177.00) and those with prior advanced CSSP only (HR 4.45, 95% CI 3.31–5.97). Risk was higher in those with prior advanced synchronous adenoma and CSSP when compared to those with prior advanced adenoma only (HR 3.19, 95% CI 2.60–3.91).

Conclusions
Patients with synchronous adenoma and CSSP may have concurrent adenoma-carcinoma and serrated pathways active, and are at higher risk of developing advanced neoplasia compared to those with only adenomas. These results may help guide surveillance colonoscopy guidelines specific for those with synchronous adenoma and CSSP.