BMJ  2005;330:1024 (30 April), doi:10.1136/bmj.330.7498.1024-b

Letter

Reduction in mortality from breast cancer

Presentation of benefits and harms needs to be balanced

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

EDITOR—Olsen et al found a 25% reduction in breast cancer mortality in Copenhagen compared with what they would expect to find in the absence of screening.¹ They did an observational study, which is not considered to be a reliable method for evaluating mortality reductions with screening.

The full mortality reduction was seen after only three years of follow-up, where it nearly reached significance, and it stayed at that level for the next seven years. However, both randomised trials and cohort studies have shown clearly that a positive effect of screening does not come that quickly. It therefore seems likely that the study has provided an exaggerated mortality benefit.

Olsen et al did not provide data on harms but refer to another of their studies when they claim that the introduction of mammography screening in Copenhagen did not lead to an increase in the incidence of breast cancer apart . . . [Full text of this article]

pcg@cochrane.dk, Nordic Cochrane Centre, Rigshospitalet Department, 7112, Blegdamsvej 9, DK-2100 Copenhagen, Denmark

Department of Health Sciences, University of Leicester

Nordic Cochrane Centre, Rigshospitalet Department, 7112, Blegdamsvej 9, DK-2100 Copenhagen, Denmark

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