Model of outcomes of screening mammography: Spontaneous regression of breast cancer may not be uncommon

doi:10.1136/bmj.331.7512.350-a

BMJ 2005;331:350 (6 August), doi:10.1136/bmj.331.7512.350-a

Letter

Model of outcomes of screening mammography

Spontaneous regression of breast cancer may not be uncommon

The first 150 words of the full text of this article appear below.

EDITOR—The model of outcomes of screening mammographyby Barratt et al proposes that more breast cancer is diagnosedamong screened than unscreened women.¹ The model predicts about40% higher cumulative incidence in women screened bienniallyduring a 10 year observation period.

Two important underlying assumptions in mammography screeningare that the sensitivity at the screening is comparatively high(> 75%) and that spontaneous tumour regression is uncommon.From these assumptions, it emerges that most of the differencein the cumulative incidences between screened and unscreenedwomen should disappear if a prevalence screening of previouslyunscreened women had been done at the end of the observationperiod.

Credit: ANDREA MOTTA/WELLCOME PHOTO LIBRARY

In particular, the model predicts that if women were followedup from 40 to 69, the cumulative 30 year difference betweenscreened and unscreened per 1000 is (17.6-13.2)+(28.1-19.8)+(32.5-23.9)= 21.3 invasive breast cancers.¹ To compensate for this . . . [Full text of this article]

Per-Henrik Zahl, senior statistician

Norwegian Institute of Public Health, PO Box 4404 Nydalen, N-0403, Oslo, Norway per-henrik.zahl@fhi.no

Jan Mæhlen, professor

Department of Pathology, Ullevål University Hospital, N-0407 Oslo, Norway

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