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Long-term risk of colorectal cancer in individuals with serrated polyps
  1. Øyvind Holme1,2,
  2. Michael Bretthauer1,2,3,4,
  3. Tor J Eide5,6,
  4. Else Marit Løberg5,6,
  5. Krzysztof Grzyb5,
  6. Magnus Løberg2,3,
  7. Mette Kalager2,4,7,
  8. Hans-Olov Adami2,4,8,
  9. Øystein Kjellevold9,
  10. Geir Hoff2,7,10
  1. 1Department of Medicine, Sørlandet Hospital, Kristiansand, Norway
  2. 2Institute of Health and Society, University of Oslo, Oslo, Norway
  3. 3Department of Transplantation Medicine, Oslo University Hospital, Oslo, Norway
  4. 4Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA
  5. 5Department of Pathology, Oslo University Hospital, Oslo, Norway
  6. 6Institute of Clinical Medicine, University of Oslo, Oslo, Norway
  7. 7Telemark Hospital, Skien, Norway
  8. 8Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
  9. 9Department of Medicine, Telemark Hospital, Kragerø, Norway
  10. 10Cancer Registry of Norway, Oslo, Norway
  1. Correspondence to Dr Øyvind Holme, Sørlandet Hospital Kristiansand, Servicebox 406, Kristiansand 4604, Norway; oyvind.holme{at}


Objective Although serrated polyps may be precursors of colorectal cancer (CRC), prospective data on the long-term CRC risk in individuals with serrated polyps are lacking.

Design In a population-based randomised trial, 12 955 individuals aged 50–64 years were screened with flexible sigmoidoscopy, while 78 220 individuals comprised the control arm. We used Cox models to estimate HRs with 95% CIs for CRC among individuals with ≥1 large serrated polyp (≥10 mm in diameter), compared with individuals with adenomas at screening, and to population controls, and multivariate logistic regression to assess polyp risk factors for CRC.

Results A total of 103 individuals had large serrated polyps, of which 81 were included in the analyses. Non-advanced adenomas were found in 1488 individuals, advanced adenomas in 701. Median follow-up was 10.9 years. Compared with the control arm, the HR for CRC was 2.5 (95% CI 0.8 to 7.8) in individuals with large serrated polyps, 2.0 (95% CI 1.3 to 2.9) in individuals with advanced adenomas and 0.6 (95% CI 0.4 to 1.1) in individuals with non-advanced adenomas. A large serrated polyp was an independent risk factor for CRC, adjusted for histology, size and multiplicity of concomitant adenomas (OR 3.3; 95% CI 1.3 to 8.6). Twenty-three large serrated polyps found at screening were left in situ for a median of 11.0 years. None developed into a malignant tumour.

Conclusions Individuals with large serrated polyps have an increased risk of CRC, comparable with individuals with advanced adenomas. However, this risk may not be related to malignant growth of the serrated polyp.

Trial registration number The Norwegian Colorectal Cancer Screening trial is registered at (NCT00119912).

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