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Effectiveness of flexible sigmoidoscopy screening in men and women and different age groups: pooled analysis of randomised trials

BMJ 2017; 356 doi: (Published 13 January 2017) Cite this as: BMJ 2017;356:i6673
  1. Øyvind Holme, postdoctoral researcher1 2,
  2. Robert E Schoen, professor3,
  3. Carlo Senore, researcher4,
  4. Nereo Segnan, professor4,
  5. Geir Hoff, professor5 6,
  6. Magnus Løberg, postdoctoral researcher2 8,
  7. Michael Bretthauer, professor1 2 7 8,
  8. Hans-Olov Adami, professor2 7 9,
  9. Mette Kalager, associate professor2 7 8
  1. 1Department of Medicine, Sorlandet Hospital Kristiansand, Kristiansand, Norway
  2. 2Clinical Effectiveness Research group, Institute of Health and Society, University of Oslo, Oslo, Norway
  3. 3Departments of Medicine and Epidemiology, University of Pittsburgh, University of Pittsburgh Cancer Institute, Pittsburgh, PA
  4. 4Centro di Prevenzione Oncologica Piemonte and Città della Salute e della Scienza University Hospital, Turin, Italy
  5. 5Telemark Hospital Skien, Skien, Norway
  6. 6Cancer Registry of Norway, Oslo, Norway
  7. 7Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA
  8. 8Department of Transplantation Medicine and KG Jebsen Center for Colorectal Cancer Research, Oslo University Hospital, Oslo, Norway
  9. 9Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
  10. Correspondence to: Ø Holme oyvind.holme{at}
  • Accepted 4 December 2016


Objective To compare the effectiveness of flexible sigmoidoscopy in screening for colorectal cancer by patient sex and age.

Design Pooled analysis of randomised trials (the US Prostate, Lung, Colorectal and Ovarian cancer screening trial (PLCO), the Italian Screening for Colon and Rectum trial (SCORE), and the Norwegian Colorectal Cancer Prevention trial (NORCCAP)).

Data sources Aggregated data were pooled from each randomised trial on incidence of colorectal cancer and mortality stratified by sex, age at screening, and colon subsite (distal v proximal).

Eligibility criteria for selecting studies Invited individuals aged 55-74 (PLCO), 55-64 (SCORE), and 50-64 (NORCCAP). Individuals were randomised to receive flexible sigmoidoscopy screening once only (SCORE and NORCCAP) or twice (PLCO), or receive usual care (no intervention).

Results 287 928 individuals were included in the pooled analysis; 115 139 randomised to screening and 172 789 to usual care. Compliance rates were 58%, 63%, and 87% in SCORE, NORCCAP, and PLCO, respectively. Median follow-up was 10.5 to 12.1 years. Screening reduced the incidence of colorectal cancer in men (relative risk 0.76; 95% confidence interval 0.70 to 0.83) and women (0.83; 0.75 to 0.92). No difference in the effect of screening was seen between men younger than 60 and those older than 60. Screening reduced the incidence of colorectal cancer in women younger than 60 (relative risk 0.71; 95% confidence interval 0.59 to 0.84), but not significantly in those aged 60 or older (0.90; 0.80 to 1.02). Colorectal cancer mortality was significantly reduced in both younger and older men, and in women younger than 60. Screening reduced colorectal cancer incidence to a similar extent in the distal colon in men and women, but there was no effect of screening in the proximal colon in older women with a significant interaction between sex and age group (P=0.04).

Conclusion Flexible sigmoidoscopy is an effective tool for colorectal cancer screening in men and younger women. The benefit is smaller and not statistically significant for women aged over 60; alternative screening methods that more effectively detect proximal tumours should be considered for these women.


  • We thank Jan Odgaard-Jensen at the Norwegian Knowledge Center for the Health Services for assistance with statistical analyses.

  • Contributors: All authors had access to all data and take responsibility for the integrity of the data. All authors contributed to the study concept and design; the acquisition, analysis, and interpretation of data; and the critical revision of the manuscript for important intellectual content. ØH performed the statistical analyses and takes responsibility for the accuracy of the data analyses (guarantor), drafting of the manuscript, statistical analysis, and funding obtained. Study supervision was by GH, RES, and CS.

  • Funding: The present work was funded by a postdoctoral grant from South-Eastern Norway Regional Health Authorities and by Sorlandet Hospital Kristiansand, Norway.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: support from South-Eastern Norway Regional Health Authorities and by Sorlandet Hospital Kristiansand for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: No ethical approval for the pooled analysis was required. Patients provided written, informed consent in the context of each trial (only screening attenders in NORCCAP). No new consent was obtained for the pooled analysis.

  • Data sharing: Data are available from the principal investigators of the individual trials on request.

  • The lead author affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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