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An independent panel of experts has concluded that breast screening saves around 1,300 lives in the UK each year.
When breast cancer is detected by screening, it generally allows for earlier treatment and an improved prognosis for the patient. However, concerns have recently been raised about over-diagnosis – where screening identifies a tumour, which is consequently treated by surgery, and often radiotherapy and medication, but which would have remained undetected for the rest of the woman’s life without causing illness if it had not been detected by screening.
The charities Breakthrough Breast Cancer, Breast Cancer Campaign and Breast Cancer Care said in a joint statement:
“This independent review has provided much-needed clarity - screening can save lives. This is good news for women as they can now be assured that breast screening can be beneficial.
"However, some women who attend screening may be diagnosed and treated for a cancer that may not have caused them harm in their lifetime. To ensure women understand what this may mean for them it is important they have access to clear and balanced information on the pros and cons of breast screening.
"As the UK’s leading breast cancer charities we are supporting the work of an expert group looking at the information women receive when invited for their screening appointments and we call for this to be available as soon as possible.
"We encourage all women to attend their screening appointments.”
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.
The panel set out to analyse the best existing evidence for the effectiveness of breast cancer screening and the risks of over-diagnosis. 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% less than those who aren’t invited to screening.
Although the panel acknowledged several limitations to these studies – not least the fact that all of them took place more than 20 years ago – they nonetheless concluded that the evidence was sufficient to allow for an overall estimated relative risk reduction of 20%.
The panel estimates that for 10,000 UK women invited to screening from age 50 for 20 years, about 681 cancers will be found of which 129 will represent over-diagnosis, and 43 deaths from breast cancer will be prevented.
According to Professor Marmot: “The reduction in risk of death from breast cancer screening corresponds to one breast cancer death prevented for every 235 women invited to screening, and one death averted for every 180 women who attend screening. The breast screening programmes in the UK, which invite women aged 50-70 years to screening every three years, probably prevent around 1,300 breast cancer deaths every year. However, our estimates also suggest that each year around 4,000 women are over-diagnosed as a result of screening.”
Read more about this in Breakthrough Breast Cancer's breast cancer screening review Q&A