Breast cancer screening leads three women to receive unnecessary treatment for every woman whose life is saved, an independent UK panel has concluded.
The panel and other commentators say that the findings should change the information that women are given about the relative risks and benefits of attending screening.
"It is now vital to give women information that is clear and accessible before they go for a mammogram so they can understand both the potential harms and benefits of the process," said Michael Marmot (University College London, UK), who led the panel, in a press release.
A meta-analysis of 11 international randomized trials, showed that the risk for breast cancer mortality was reduced by 20% in women who were screened compared with women who were not.
However, when the panel reviewed evidence on overdiagnoses, they concluded that these represent 19% of cancers diagnosed in women between the ages of 50 and 69 years during screening.
The panel estimated that this translates to around 4000 women each year being overdiagnosed in the UK, while screening prevents 1300 deaths.
The panel ‑ comprising experts with no prior publications on breast screening to increase impartiality ‑ was formed in response to continued controversy over the benefits of breast screening.
The panel concluded in The Lancet that, despite the risk for overdiagnosis, the evidence supported the UK's breast screening program because early detection and treatment result in reduced breast cancer mortality.
Speaking to medwireNews, Greg Rubin, from the charity Cancer Research UK, described the review as "authoritative" and said it should help patients to make informed decisions. "It quantifies for us the risks and the benefits of breast screening, providing clear figures that will be useful for GPs [general practitioners] when they're talking to patients who may be concerned about whether or not to participate."
Margaret McCartney, a practicing GP in Glasgow, UK, told medwireNews that it was fundamental for women to make their own decisions about whether to attend screening: "It has always been clear that screening has downsides and women have been badly served by the blanket encouragement to be screened rather than to make a properly informed choice."
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