Breast screening ‘is beneficial’
Breast cancer screening does more good than harm, with any over-treatment justified by the number of lives saved, say experts.
Mammograms can spot dangerous tumours, but might also detect lumps that are essentially harmless, exposing some women to undue anxiety and surgery.
But data suggests screening saves the lives of two women for every one who receives unnecessary treatment.
The study of 80,000 women appears in the Journal of Medical Screening.
The research, by experts from the Wolfson Institute of Preventive Medicine at Barts and the London School of Medicine and Dentistry, estimated that 5.7 breast cancer deaths were prevented for every 1,000 women screened over a 20-year period.
At the same time, 2.3 women per 1,000 were told they had a lump but it was not clear if it was an aggressive form of cancer that needed to be treated.
Put another way, for every 28 cases diagnosed, 2.5 lives were saved and one case was over-diagnosed.
‘Significant reduction’
Women aged 50 to 70 are invited for NHS breast screening every three years across the UK.
Previous research has cast doubt on the benefits of screening women for breast cancer, and it is a debate that is ongoing among experts.
England’s NHS screening programme has been rewriting its leaflet for patients after concerns it did not provide enough explanation for women about their choices.
A new version of the leaflet will be published by this summer.
But the authors of this latest study say the benefits of breast screening are clear.
"The benefits in terms of numbers of deaths prevented are around double the harm in terms of over-diagnosis.
"Analysis shows a substantial and significant reduction in breast cancer deaths in association with mammographic screening," they said.
‘Compelling argument’
Richard Winder, deputy director of NHS cancer screening programmes, said: "There is a risk of over-diagnosis, and possible subsequent over-treatment, associated with any screening programme.
"But this latest independent study shows that the risk of over-diagnosis is very much lower than some other recent estimates have claimed, and that the benefits far outweigh the risks."
Dr Alexis Willett, head of policy at Breakthrough Breast Cancer, said the new research provided a compelling argument in favour of breast screening.
"Screening saves lives because it picks up cancer before any symptoms can be seen or felt.
"The earlier cancer is diagnosed, the better a woman’s chance of a successful outcome," she said.
Emma Pennery, clinical director at Breast Cancer Care, said they were aware the ongoing debate over the effectiveness of screening could cause "confusion and anxiety for women".
"This robust study clearly reinforces that screening remains an effective option for detecting breast cancers," she said.
Jayant Vaidya, a breast cancer surgeon at University College London and the Whittington Hospital, said the study was based on calculations that were opaque.
"Women who go for breast cancer screening need to know that there’s a good chance they could be diagnosed with a cancer which is not harmful and may never have bothered them," he said.
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