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Breast cancer screening "reduces deaths, but over-diagnoses"

Experts say that in some cases, women are diagnosed with tumours that would have remained undetected for the rest of their lives and which they would not have died from.

Image: Michael Probst/AP/Press Association Images

AN INDEPENDENT UK review has found that breast cancer screening reduces deaths, but can also result in over-diagnoses.

An independent panel of experts concluded that routine breast cancer screening results in a reduced risk of dying from breast cancer compared to when no screening takes place, but that screening also results in over-diagnosis, according to a review published in The Lancet.

Concerns raised

Concerns have recently been raised about over-diagnosis. This is where the screening identifies a tumour, which is consequently treated by surgery, and often radiotherapy and medication. However, this tumour would have remained undetected for the rest of the woman’s life without causing illness if it had not been detected by screening.

The panel, led by Professor Sir Michael Marmot, Director of the Institute of Health Equity at University College, London, UK, was set up by The National Cancer Director for England, Professor Sir Mike Richards, and Dr Harpal Kumar, Chief Executive Officer of Cancer Research UK, to provide an independent review of the evidence for the benefits and harms of breast cancer screening in the UK.

They performed a meta-analysis of 11 randomised controlled trials assessing whether breast cancer screening results in fewer deaths due to the disease, compared to when no screening takes place.

Overall, they found that women who are invited to breast cancer screening have a relative risk of dying from breast cancer that is 20 per cent less than those who aren’t invited to screening.

Although the panel acknowledged several limitations to these studies, they concluded that the evidence was sufficient to allow for an overall estimated relative risk reduction of 20 per cent.

Overdiagnosis

They reported a scarcity of reliable studies on over-diagnosis, but the panel concluded that for the roughly 307 000 women aged 50-52 years who are invited to begin screening every year, just over 1 per cent will have an over-diagnosed cancer in the next 20 years.

For 10,000 UK women invited to screening from age 50 for 20 years, they estimate that about 681 cancers will be found, of which 129 will represent over-diagnosis, and 43 deaths from breast cancer will be prevented.

However, the panel state that the figures quoted give “a spurious impression of accuracy”, and further research will be needed.

According to Professor Marmot, clear communication of these harms and benefits to women is essential, and the core of how a modern health system should function.

Ireland

The National Cancer Screening Service (NCSS) which encompasses BreastCheck – The National Breast Screening Programme today welcomed the findings of the NHS breast screening programme review.

It said it:

supports the finding that it is 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.
At present women who would like more detailed information about DCIS (Ductal Carcinoma in Situ) and the benefits and limits of breast screening are directed to the BreastCheck Freephone information line or the website for a detailed factsheet.

Its leaflets advise that women of any age can get breast cancer – but that the risk increases with age, that not all breast cancers can be found by a mammogram, that some women may find the mammogram painful and that some non-invasive cancers (known as DCIS) will be found by screening.

BreastCheck provides free mammograms to women aged 50-64 on an area-by-area basis every two years. The aim of BreastCheck is to detect breast cancers at the earliest possible stage. At this early stage, a woman has greater treatment options available to her and her chosen treatment is likely to be less extensive and more successful.

Read: Misdiagnosed cancer patient Olive Fahey: ‘Don’t be afraid to insist on going elsewhere’>

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