712 Flat Colonic Neoplasia Are Left Undetected By Fecal Immunochemical Tests (FIT) and Will Be Missed in Colorectal Cancer Screening

with 10,492 patient-years of follow-up. One hundred ninety patients (26.6%) had at least one adenoma at baseline, of which 38 (20%) had 3 or more adenomas, 22 (12%) had an adenoma 1 cm or larger, 25 (13%) had an adenoma with villous histology, and 2 (1%) had an adenoma with high-grade dysplasia. Patients with adenomas at baseline underwent 714 surveillance colonoscopies over 2,685 person-years of follow-up, equivalent to one procedure every 3.8 years. Patients without adenomas at baseline underwent 1401 colonoscopies over 7,745 person-years of follow-up, equivalent to one procedure every 5.5 years (p<0.0001). There were 12 cases of CRC, 5 found at baseline and 7 after a median follow-up of 8 years (range 3 to 16 years). There were 7 incident cases of CRC (95% CI: 2-13) for an incidence rate of 0.77 cases per 1,000 person-years, and a SIR of 0.33 (95% CI: 0.10-0.62). During the study follow-up period, 3 patients died of CRC (95% CI 0-9), for a mortality rate of 0.29 per 1,000 person-years and a SMR of 0.35 (95% CI: 0.0-1.06). Conclusions: In this average-risk cohort, colorectal cancer incidence and mortality were reduced after screening colonoscopy. These results provide evidence for the effectiveness of colonoscopy as a primary CRC screening modality.