title: Natural history of diminutive and small colorectal polyps: a systematic literature review.
abstract: OBJECTIVE
  Diminutive (1-5 mm) and small (6-9 mm) polyps comprise 90% of detected lesions during colonoscopy and rarely contain advanced histology or colorectal cancer (CRC). Routine removal of these lesions results in a significant burden to colonoscopy programs. At the same time, the risk for progression of these polyps to CRC is unclear. We performed a systematic review to explore the natural history of diminutive and small colorectal polyps.
  
  
  METHODS
  We searched MEDLINE and EMBASE for studies investigating the natural history of colorectal polyps. Studies were considered eligible when they assessed patients with 1- to 9-mm polyps that were not treated with polypectomy and that underwent follow-up. We excluded studies in patients with inflammatory bowel disease, polyposis syndromes, and previously diagnosed CRC. We independently extracted study characteristics and evaluated CRC and advanced adenoma (size ≥ 10 mm, containing high-grade dysplasia or villous features) as outcome parameters.
  
  
  RESULTS
  Of 8775 retrieved studies, 9 studies with 721 patients were included that prospectively evaluated the evolution of 1- to 9-mm polyps. In 7 studies the average duration of observation was 2 to 3 years. There was only 1 study in which 1 small polyp might have progressed to cancer. Of 1034 adenomas sized 1 to 9 mm in those studies, 6% progressed to advanced adenomas over time.
  
  
  CONCLUSIONS
  Based on this systematic review, it appears that some 1- to 9-mm adenomas progress to advanced adenomas within 2 to 3 years. No information on long-term CRC transition rates was found. Defining the biologic significance of these polyps is needed to balance between benefits and harm of polypectomy. (PROSPERO database registration number: CRD42016036577.).
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Jasper L A
authors.initials: JLA
authors.lastname: Vleugels
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Yark
authors.initials: Y
authors.lastname: Hazewinkel
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Fockens
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Evelien
authors.initials: E
authors.lastname: Dekker
mesh_terms: D000236:Adenoma / Q000473:pathology*; D002277:Carcinoma / Q000473:pathology; D003111:Colonic Polyps / Q000473:pathology*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D007417:Intestinal Polyps / Q000473:pathology; D047368:Tumor Burden