Introduction: Sessile serrated adenomas (SSAs) are premalignant colorectal serrated polyps (SPs) that are increasingly recognized on screening colonoscopy. The risk of metachronous neoplasia associated with SSAs is uncertain. We aimed to determine the risk of future neoplasia in patients with SSAs vs. other polyp types on index colonoscopy. Methods: We identified patients undergoing colonoscopy between 1998 and 2010 at the University of North Carolina with conventional adenomas (CAd), SPs, and normal exams. Proximal and large SPs were reviewed by an expert pathologist to determine the presence of SSAs. Medical records were reviewed to determine findings of all subsequent colonoscopies through January 2015. Findings of colonoscopy and pathology reports were abstracted to determine presence of polyps and high risk adenomas (HRA, defined as CAd ≥10mm, with villous features or high grade dysplasia, or ≥3 CAd). Multivariable logistic regression was performed to estimate ORs and 95% CI for any CAd, HRA, or subsequent SSA in each polyp group, compared to those with no polyps, adjusting for age, sex, study, and year of colonoscopy. Results: We identified 1316 (57%) without polyps, 460 with CAd only (20%), and 78 patients with SSAs in a population of 2308 patients undergoing colonoscopy. 600 (45.6%) of the total population had at least 1 subsequent colonoscopy and were included in this analysis, including 54 patients with baseline SSAs. Those with only CAd had an elevated risk of recurrent adenomas and HRA compared to those with no polyps [OR: 1.72 (95% CI 1.12, 2.63) and OR: 3.06 (95% CI 1.38, 6.81), respectively]. Those with hyperplastic polyps (HP) had the same risk of subsequent HRA as those without polyps. Those with baseline SSAs had an increased risk of subsequent HRA and SSAs compared to those without baseline polyps, but this did not reach statistical significance [OR: 2.06 (0.52, 8.14) and OR: 4.38 (95% CI 0.66, 29.10), respectively]. The OR estimates for metachronous CAd and HRA were lower in those with baseline SSAs vs. those with CAd. Conclusion: In this study, we found that SSAs on baseline colonoscopy were associated with roughly 2-fold increase in risk of metachronous HRA compared to those without polyps, but this was not statistically significant. Our numbers were small, limiting precision of these estimates, especially for SSA group. Further research is needed on the natural history of patients with SSAs in order to better inform surveillance guidelines.Table 1: Risk of metachronous neoplasia associated with sessile serrated adenomas and other polyp types