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Breast cancer report prompts change in NHS guidance on overdiagnosis risk

The Department of Health has said it will revise the advice it gives to women before breast cancer screening, following a report showing the programme prevents deaths, but also results in overdiagnosis.

The meta-analysis of evidence found women who are invited to a breast cancer screening had a 20% reduced relative risk of dying from breast cancer compared with women who aren’t invited to screening.

But they also found the chance of overdiagnosis was just over 1% for the roughly 307, 000 women aged 50 to 52 years who are invited to begin screening every year.

Jointly-commissioned by Cancer Research UK and the DH, the independent panel concluded that the benefits of early detection and treatment with screening outweighed the harms, but added that women should be made aware of the risks so they can make an informed decision.

The report has led to a review of the information provided by the NHS when women are invited for screening.

The panel conducted a meta-analysis of 11 randomised control trials assessing whether breast cancer screening resulted in fewer deaths and the evidence for over-diagnosis, compared with no screening.

Although they acknowledged that there were limitations to the studies- all of which took place more than 20 years ago - they found the current breast cancer screening programme, which invites all women aged 50 to 70 years to screening every three years, prevented about 1,300 deaths from breast cancer a year.

It also found that each year around 4,000 breast cancers are overdiagnosed- with women receiving treatments such as surgery, radiotherapy and medication for cancers that may not have come to clinical attention in the woman’s lifetime were it not for screening.

The panel estimated that for the 10,000 women invited to screening from age 50 for 20 years, about 681 cancers will be found.  Of those, 129 represent overdiagnosis, and 43 deaths will be prevented.

Study author Sir Michael Marmot, director of the Institute of Health Equity at University College, London concluded: ‘The UK breast screening programmes confer significant benefit and should continue.

‘For each woman, the choice is clear.  On the positive side, screening confers a reduction in the risk of mortality of breast cancer because of early detection and treatment. 

‘On the negative side, is the knowledge that she has perhaps a 1% chance of having a cancer diagnosed and treated that would never have caused problems if she had not been screened. 

He added: ‘Clear communication of these harms and benefits to

women is essential and is the core of how a modern health system should function.’

Professor Sir Mike Richards, National Cancer Director, said NHS Cancer Screening Programmes will now look at the ways in which they can best communicate the findings of the review so that women can make an informed decision about screening.

He said: ‘The key thing is that we communicate this new information to women so they can make an informed choice for themselves. NHS Cancer Screening Programmes have already asked independent academics to develop new materials to give the facts in a clear, unbiased way.

‘I hope to see them in use in the next few months. If any woman has concerns about breast screening she should talk to her GP or health professional.’

The study comes after a European-wide analysis found that on average, for every 1,000 women screened for breast cancer every two years from aged 50 to around 69, an estimated seven to nine lives were saved and four cases were over-diagnosed.

The panel warned that these figures should be considered as the best estimates from inadequate data, and that further research is needed to accurately assess the benefits and harms of screening.

Dr Phil Sawyer, a GP in St Alban’s, Herfordshire, and Mount Vernon Cancer Network primary care lead, said the most important thing was that patients are made aware of the potential harms of screening in an understandable form so they can make an informed choice.

He said: ‘The breast cancer screening programme will need to review it’s communications with women in light of this new paper to ensure that they make decisions to participate based on a full understanding of the risks and benefits.’