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Education And Debate

Mammography and the politics of randomised controlled trialsCommentary: The public has a role to play in translating evidence into practiceCommentary: Why are researchers surprised when there is not a smooth transition from research into practice?

BMJ 1998; 317 doi: (Published 31 October 1998) Cite this as: BMJ 1998;317:1224

Mammography and the politics of randomised controlled trials

  1. Jane Wells, specialist registrar in public health medicine (
  1. Health Services Research Unit, Department of Public Health, Institute of Health Sciences, University of Oxford, Oxford OX3 7LF
  2. Division of Public Health and Primary Care, University of Oxford, Institute of Health Sciences, Oxford OX3 7LF
  3. Consumers' Health of Australia, PO Box 52, Lyons ACT 2606, Australia

    The purpose of screening mammography is to reduce mortality in women who develop breast cancer by detecting it at a stage when treatment is most likely to be effective. Mammography has been more extensively evaluated by randomised controlled trials than any other screening intervention but its effectiveness in some groups of women remains controversial.

    x Ray examination of the breast has been used since the beginning of this century; initially for diagnosis and later for the detection of non-palpable lesions. By the early 1960s results from mammography had been shown to be sufficiently reliable to prompt the United States National Cancer Institute to begin a trial of its use as a screening procedure. Organisations in the United States involved in assessing the effectiveness of mammography are described in the box.

    Summary points

    Randomised controlled trials of the effectiveness of screening mammography have found that it significantly reduces mortality in women over 50 but that the benefit is smaller, and the associated harm is greater, in younger women

    In the United States many organisations have issued guidelines on screening for women aged 40-49, some groups recommend that they should be screened regularly and others that they should not

    In January 1997 a consensus conference convened by the National Cancer Institute did not advise routine screening but recommended that women reach their own decision in consultation with their doctor

    Many politicians, professional and voluntary groups, and individuals (including some healthcare professionals, journalists, women with breast cancer, and researchers) disagreed with this recommendation, and pressure was exerted on the National Cancer Institute to recommend regular screening for all women aged 40-49; in March 1997 the institute issued guidelines recommending regular screening for this age group

    Political involvement and public expectations can impede the appropriate translation of research findings into clinical practice

    US organisations involved in assessing the effectiveness of mammography

    National Institutes of Health …

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