Microbiota-assisted screening for colorectal neoplasia: advanced adenoma as the key translational endpoint-a...

Microbial differences between established colorectal cancer (CRC) and cancer-free controls are reproducible, but screening translation depends on detecting advanced adenoma and early CRC in asymptomatic populations. We examined the gut microbiota as an adjunct to fecal immunochemical testing (FIT), stool deoxyribonucleic acid (DNA) testing, and colonoscopy, with advanced adenoma as the prevention-relevant endpoint. This narrative review used a structured, purposive search of PubMed, Embase, Web of Science, Scopus, and the Cochrane Library through April 10, 2026, prioritizing human neoplasia cohorts, stage-specific biomarkers, multi-omics studies, FIT comparators, and reporting standards. Across studies, microbial signals were strongest for established CRC and weaker and less consistently reported for advanced adenoma. Quantitative evidence supports selected adjunctive approaches, including fecal Fusobacterium nucleatum and multitaxon panels combined with FIT, but external validation remains sparse. The 2025 pooled analysis of 3,741 metagenomes demonstrated reproducible CRC-related features across 18 cohorts but did not report advanced-adenoma-specific accuracy. Clinical utility cannot be inferred from sensitivity, specificity, or the area under the receiver operating characteristic curve alone: prevalence-dependent positive predictive value (PPV), negative predictive value (NPV), calibration, a prespecified action threshold, decision-curve net benefit, and colonoscopy burden are decisive. Translation therefore requires a locked assay and model tested prospectively before bowel preparation in a representative screening cohort, with advanced adenoma reported separately and performance compared directly with FIT or stool DNA testing. Microbiota-based markers currently merit evaluation as adjuncts, not replacements, within established screening pathways.