Whether diminutive or small adenomas detected by fecal immunochemical tests (FITs) are associated with a higher risk of advanced histology remains unknown. We investigated the prevalence of advanced histology in diminutive and small adenomas detected by FIT and compared with that detected by colonoscopy screening.
We prospectively compared 1,860 FIT-positive patients (FIT-positive cohort) and 6,691 average-risk patients (screening colonoscopy cohort). Both groups underwent colonoscopies and were shown to have neoplastic lesions. The prevalence of advanced histology was determined, as was the associations with size and FIT positivity.
We analyzed 3,920 neoplastic lesions from the FIT-positive cohort and 9,789 neoplastic lesions from the screening colonoscopy cohort. Eighty (4.3%) diminutive lesions in FIT-positive cohort had advanced histology but without any invasive cancer. Twenty-one patients in the FIT-positive cohort and 49 in the screening colonoscopy cohort with diminutive adenomas displayed advanced histology (3.5% vs. 1.2%; adjusted odds ratio[aOR]=2.99, 95% confidence interval [CI]: 1.77-5.06). Sixteen patients in the FIT-positive cohort (2.7%) with diminutive adenomas might have changed the surveillance interval if a resect-and-discard strategy was applied, with a higher likelihood compared with the screening colonoscopy cohort (aOR=2.76, 95% CI: 1.53-4.99).
FIT screening detected more diminutive and small adenomas with advanced histology compared with colonoscopy screening. Its impact on current management of diminutive polyp is limited.

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