S636 Risks of Advanced Adenomas and Colorectal Cancers in Patients With Negative Versus Positive Fecal Immunochemical Tests and Implications in Clinical Practice: Real-World Experience From Urban Public Hospitals

Introduction: The United States Preventive Services Task Force (USPSTF) lowered the age of colorectal cancer screening to 45 years old in 2021, which greatly increased the demand for colonoscopy. In US public hospitals that serve underprivileged populations, the waiting time for colonoscopy often is up to 1 year and primary care providers may send a fecal immunochemical test (FIT) while waiting. Methods: We retrospectively examined colonoscopy results from patients in 2 urban public hospitals who previously received FIT testing, focusing on the risk of colorectal cancer and advanced adenoma, which has high risk of progression into cancer if not removed. Results: A total of 439 FIT-negative and 137 FIT-positive patients were included. Significantly higher detection rates of advanced adenoma (21.2% vs 4.3%, P < 0.001) and colorectal cancer (5.1% vs 0.5%, P = 0.001) were found in FIT-positives. Two (0.5%) FIT-negative patients were found to have cancer but both had significant anemia (HGB 7.8 and 8.6 g/dL). No significant differences were found in the risks of nonadvanced adenomas (29.9% vs 24.8%, P = 0.235) or hyperplastic polyps (19% vs 18.7%, P = 0.938). Among patients without symptoms (rectal bleeding, refractory constipation, and weight loss) or anemia, cancer was detected in 3 patients, all tested positive for FIT, and 20.5% of FIT-positive patients as well as 3.2% of FIT-negative patients were found to have advanced adenoma (P < 0.001), equivalent to a negative predictive value of 96.8%. For FIT-negative patients, when comparing those who received colonoscopy within 1 year and those who received colonoscopy between 1-2 years, no significant difference was found in the detection rate of advanced adenoma (4.6% vs 4.1%, P = 0.823). Among FIT-negative patients, no difference was found in FIT to colonoscopy interval between those who had advanced adenoma vs those who did not (313 (210-440.5) days vs 267.5 (144-448) days, P = 0.6). No difference was found among FIT-positive patients, either (84 (55-164) days vs 80.5 (53-137.5) days, P = 0.889). Conclusion: The negative predictive value of FIT results (96.8% in asymptomatic patients) in our patient population is similar to previous reports (93.6-96.6%). FIT cannot effectively detect nonadvanced adenomas or hyperplastic polyps. Simultaneously ordering FIT and colonoscopy may not be necessary. Interval between FIT and colonoscopy (1 vs 2 years) did not affect the risk of advanced adenoma. Routine FIT frequency can be reduced to every 2 years.