title: Overview of guidelines on breast screening: Why recommendations differ and what to do about it.
abstract: Updated guidelines on breast cancer screening have been published by several major organisations over the past five years. Recommendations vary regarding both age range, screening interval, and even on whether breast screening should be offered at all. The variation between recommendations reflects substantial differences in estimates of the major benefit (breast cancer mortality reduction) and the major harm (overdiagnosis). Estimates vary considerably among randomised trials, as well as observational studies: from no benefit to large reductions, and from no overdiagnosis to substantial levels. The estimates vary according to the methodology of the randomised trials, and the design of the observational studies. Guideline recommendations reflect the choice of evidence informing them. While there are well-developed tools to deal with randomised trials in guideline work, these are not always used, or they may not be followed as recommended. Further, results of trials performed decades ago may no longer be applicable. For observational studies, the framework for inclusion in guidelines is not similarly well-developed and there are methodological concerns specific to screening interventions, such as small effects in absolute terms. There is a need for agreement on a hierarchy of observational study designs to quantify the major benefit and harm of cancer screening. This review provides a summary of recent guidelines on breast cancer screening and their major strengths and weaknesses, as well as a short overview of the major strengths and limitations of observational study designs. There is a need for agreement on a hierarchy of observational study designs in this field.
authors.affiliation: The Nordic Cochrane Centre, Rigshospitalet Department 7811, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. Electronic address: kj@cochrane.dk.
authors.forename: Karsten Juhl
authors.initials: KJ
authors.lastname: Jørgensen
authors.affiliation: University of Oslo, Institute of Health and Society, Department of Health Management and Health Economics, P.O. Box 1089, Blindern, 0318 Oslo, Norway; Department of Transplantation Medicine and KG Jebsen Center for Colorectal Cancer Research, Oslo University Hospital, Oslo, Norway; Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA.
authors.forename: Mette
authors.initials: M
authors.lastname: Kalager
authors.affiliation: School of Public Health, University of Sydney, NSW 2006, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Barratt
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Baines
authors.affiliation: Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, N-0403 Oslo, Norway.
authors.forename: Per-Henrik
authors.initials: PH
authors.lastname: Zahl
authors.affiliation: Research Unit for General Practice and Section of General Practice, Department of Public Health, University of Copenhagen, Copenhagen & Primary Health Care Research Unit, Zealand Region, Denmark.
authors.forename: John
authors.initials: J
authors.lastname: Brodersen
authors.affiliation: University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Russell P
authors.initials: RP
authors.lastname: Harris
mesh_terms: D000367:Age Factors; D000570:American Cancer Society; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D055088:Early Detection of Cancer / Q000009:adverse effects / Q000592:standards*; D005260:Female; D006801:Humans; D008327:Mammography; D009664:Norway; D064887:Observational Studies as Topic; D017410:Practice Guidelines as Topic; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D013557:Switzerland; D006113:United Kingdom; D014481:United States
keywords: Breast cancer screening; Cancer epidemiology; Guideline development