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Risk of colorectal cancer seven years after flexible sigmoidoscopy screening: randomised controlled trial

BMJ 2009; 338 doi: (Published 31 May 2009) Cite this as: BMJ 2009;338:b1846
  1. Geir Hoff, professor12,
  2. Tom Grotmol, professor 1,
  3. Eva Skovlund, professor 3,
  4. Michael Bretthauer, physician and researcher14,
  5. for the Norwegian Colorectal Cancer Prevention Study Group
  1. 1Norwegian Colorectal Cancer Prevention (NORCCAP) Centre, Cancer Registry of Norway, Montebello, NO-0310 Oslo, Norway
  2. 2Department of Medicine, Telemark Hospital, NO-3710 Skien, Norway
  3. 3School of Pharmacy, University of Oslo, NO-0316 Oslo
  4. 4Department of Gastroenterology, Rikshospitalet University Hospital, NO-0027 Oslo
  1. Correspondence to: G Hoff, Cancer Registry of Norway, P O Box 5313 Majorstuen, 0304 Oslo, Norway hofg{at}
  • Accepted 8 April 2009


Objective To determine the risk of colorectal cancer after screening with flexible sigmoidoscopy.

Design Randomised controlled trial.

Setting Population based screening in two areas in Norway—city of Oslo and Telemark county (urban and mixed urban and rural populations).

Participants 55 736 men and women aged 55-64 years.

Intervention Once only flexible sigmoidoscopy screening with or without a single round of faecal occult blood testing (n=13 823) compared with no screening (n=41 913).

Main outcome measures Planned end points were cumulative incidence and mortality of colorectal cancer after 5, 10, and 15 years. This first report from the study presents cumulative incidence after 7 years of follow-up and hazard ratio for mortality after 6 years.

Results No difference was found in the 7 year cumulative incidence of colorectal cancer between the screening and control groups (134.5 v 131.9 cases per 100 000 person years). In intention to screen analysis, a trend towards reduced colorectal cancer mortality was found (hazard ratio 0.73, 95% confidence interval 0.47 to 1.13, P=0.16). For attenders compared with controls, a statistically significant reduction in mortality was apparent for both total colorectal cancer (hazard ratio 0.41, 0.21 to 0.82, P=0.011) and rectosigmoidal cancer (0.24, 0.08 to 0.76, P=0.016).

Conclusions A reduction in incidence of colorectal cancer with flexible sigmoidoscopy screening could not be shown after 7 years’ follow-up. Mortality from colorectal cancer was not significantly reduced in the screening group but seemed to be lower for attenders, with a reduction of 59% for any location of colorectal cancer and 76% for rectosigmoidal cancer in per protocol analysis, an analysis prone to selection bias.

Trial registration Clinical trials NCT00119912.


  • We thank Mette Kalager, Bjarte Aagnes, Odd Aalen, Steinar Tretli, Tor Haldorsen, and Freddie Bray for valuable discussions, as well as the Norwegian Colorectal Cancer Prevention (NORCCAP) trial staff for enthusiastic assistance.

  • The NORCCAP Study Group comprises Michael Bretthauer, Erik Carlsen, Tor Jac Eide, Tom Grotmol, Geir Hoff, Tor Iversen, Stener Kvinnsland, Frøydis Langmark, Jon Lekven, Jørn Schneede, Eva Skovlund, Kjell Magne Tveit, and Morten Vatn.

  • Further collaborators were Knut Bjerke, Per Efskind, Ghous Gondal, Kai Brynjar Hagen, Gert Huppertz-Hauss, Yngve Haugstvedt, Bjørn Hofstad, Solveig Thorp Holmsen, Anita Jørgensen, Inger Kristin Larsen, Per G Lund-Larsen, Idar Lygren, Volker Moritz, Sverre Nyhus, Odd Søreide, Espen Thiis-Evensen, Lisbeth Tranebjærg, Aage Tverdal, Per Wium, and Lars Ødegård.

  • The NORCCAP external advisory committee comprises Hans-Olov Adami, Sandra J Lee (both Harvard School of Public Health, Boston, USA), and Douglas K Rex (Indiana University School of Medicine, Indianapolis, USA).

  • Contributors: GH, TG, and ES planned the study together with members of the NORCCAP Study Group. Together with MB, they drafted and refined the manuscript. All four authors also contributed to the statistical analysis with full access to all data. All authors wrote and approved the final draft of the manuscript. Frøydis Langmark (director, Cancer Registry of Norway, Oslo) is the guarantor.

  • Funding: NORCCAP trial 1 was funded by grants from the Norwegian Cancer Society and the Norwegian Ministry of Health. The authors are independent from the funders of the NORCCAP trial 1.

  • Competing interests: None declared.

  • Ethical approval: The regional committee for medical research ethics and the Norwegian Data Inspectorate approved the NORCCAP trial 1 protocol. All participants in the screening group have been informed about the nature and purpose of the study, and all those who attended screening provided written informed consent in advance.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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