S288 Missed High-Risk Adenomas and Colorectal Cancers Due to COVID-19 Pandemic at an Urban U.S. Tertiary Care Center in 2020

Introduction: During the COVID-19 pandemic, outpatient colonoscopies throughout the US were postponed, creating a significant backlog of procedures. We estimated the number of missed high- risk adenomas and colorectal cancers in 2020 at an urban, tertiary-care, safety-net teaching hospital in Boston, Massachusetts. Methods: This observational study evaluated the number of high-risk adenomas (defined as ≥3 adenomas, adenoma ≥10 mm in size, adenoma with tubulovillous or villous histological features, or adenoma with high-grade dysplasia) and colorectal cancers diagnosed by outpatient colonoscopy from January 2020 to November 2020, and compared it with those diagnosed from January 2017 to December 2019. Patients with a personal history of colorectal cancer or a colonoscopy indication of inflammatory bowel disease, therapeutic procedure (other than removal of large polyp), or diarrhea were excluded (10% of all colonoscopies). A Poisson regression model using colonoscopy data from 2017 to 2019-adjusted for age, sex, race/ethnicity and indication-was used to predict expected highrisk adenomas and colorectal cancers per month in 2020. Predicted values were compared to actual values to estimate missed diagnoses. Results: A total of 6597, 7136, and 6816 colonoscopies were performed in 2017, 2018 and 2019, respectively. There were 40% fewer colonoscopies performed in January to November 2020 (n = 3704) compared to the same period in 2019. In January to November 2020, 505 high-risk adenomas (Figure 1a) and 21 colorectal cancers (Figure 1b) were diagnosed. We estimate that 284 (36%) highrisk adenomas and 9 (30%) colorectal cancers were missed during this period. The rate of colorectal cancer detection was 6 per 1000 cases performed in 2017 to 2019. Assuming similar patient characteristics and indications, 1349 additional colonoscopies will be needed to diagnose 9 missed colorectal cancers. Conclusion: This study provides one of the first real world estimates of missed high-risk adenomas and colorectal cancers due to the cancellation of outpatient colonoscopies during the COVID-19 pandemic. The results have implications on planning strategies to schedule elective colonoscopies to increase the yield of detection of these high-risk lesions.