Letters
Cancer
Volume 196 - Issue 11

Do the benefits of screening mammography outweigh the harms of overdiagnosis and unnecessary treatment?

Authors:  Alexandra L Barratt and Paul P Glasziou

Med J Aust 2012; 196 (11): 681. || doi: 10.5694/mja12.10236
Published online: 18 June 2012
To the Editor: Although both sides of the debate about screening mammography1,2 acknowledge the mortality benefit due to screening and the risk of overdiagnosis, the magnitude and relative value of these need further clarification and reflection. In calculating the number of breast cancer deaths averted using a relative risk reduction of 35%, Roder and Olver overstate the benefit. Other estimates of effect are lower (eg, ...
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To the Editor: Although both sides of the debate about screening mammography1,2 acknowledge the mortality benefit due to screening and the risk of overdiagnosis, the magnitude and relative value of these need further clarification and reflection. In calculating the number of breast cancer deaths averted using a relative risk reduction of 35%, Roder and Olver overstate the benefit. Other estimates of effect are lower (eg, 15%,3 16% [all ages] and 22% [> 50 years],4 and 19%5) and lead to a calculation of fewer averted deaths.

Roder and Olver also call for more research on overdiagnosis. That research has been done6-8 — the increase in incidence is impressive and most marked in women of screening age (Box).6 While contributing factors include a background increase in breast cancer incidence, changes in risk factors (reproductive behaviour, weight and hormone therapy) and screening lead time, an analysis of the New South Wales data that accounted for these factors found overdiagnosis in 30%–40% of apparent cancers detected among women screened, accounting for about one in four of all invasive breast cancers diagnosed in the state.6 International estimates using recent observational data are similar.7,8

Although there is residual uncertainty, more research will not resolve the central dispute about whether the benefit outweighs the harm. It is simply a value judgement. We already have enough evidence to decide — but the central issue now is who should make the decision. Policymakers, experts, or the women potentially engaged in screening? Until we have some form of proper informed “consent” from the target population, we must stop promoting breast cancer screening with information that overstates the benefit and understates the harm.

Mean annual age-specific breast cancer incidence in women before universal health insurance (Medicare) (1972–1983) and under established organised mammography screening (1999–2001 and 2004–2006) in New South Wales6

Authors

  • Alexandra L Barratt1
  • Paul P Glasziou2
  • 1. Sydney School of Public Health, University of Sydney, Sydney, NSW.
  • 2. Faculty of Health Sciences, Bond University, Gold Coast, QLD.

Correspondence: alexb@health.usyd.edu.au

Competing interests

No relevant disclosures.

References

View this article on Wiley Online Library

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