What the breast screening review means
This page is about the findings of the Breast Screening Review Panel. There is information on
- What breast screening is
- The background to breast screening in the UK
- Why the review was carried out
- Who was on the panel
- The known benefits of screening
Screening means looking for early signs of a particular disease in healthy people who don’t have any symptoms. Screening for cancer aims to find cancers as early as possible - when the chance of cure is highest. Breast screening means using tests to find breast cancers as early as possible, before they cause symptoms such as a lump in the breast.
The UK breast screening programme uses mammograms to screen for breast cancer in women every 3 years between the ages of 50 and 70. A mammogram is a specialised X-ray of the breast.
After a mammogram, women who have signs of something unusual are called back for more tests (a biopsy), to confirm or rule out breast cancer.
If a diagnosis is confirmed, women are offered breast cancer treatment. Out of all the women who have breast cancer found through screening, more than 99 out of every 100 women (99%) have surgery. About 87 out of every 100 (87%) have hormone therapy. 80 out of every 100 (80%) have radiotherapy. And about 26 out of every 100 (26%) have chemotherapy.
The NHS Breast Screening Programme was the first of its kind in the world. It began inviting women for screening in 1988 and covered the whole of the UK by the mid 1990s.
The programme is currently being expanded and will offer mammograms to women between the ages of 47 and 73. Women over 73 can request screening every 3 years by contacting their local breast screening unit.
The breast screening review was set up after concerns were raised that women were being told a lot about the possible benefit and not enough about the possible harm. With different experts speaking out both in favour and against breast screening, a public review was needed to help get to the true picture. The Government and Cancer Research UK asked a world-renowned statistician, Professor Sir Michael Marmot, to chair an independent Panel to review the evidence.
The aim of the review was to have a group of independent experts weigh up all the evidence about the pros and cons of breast screening. Then it would be possible to make sure that women could be given the clearest picture possible to help them decide whether to have breast screening or not.
The panel included a breast cancer patient experienced in representing the needs of cancer patients, and experts in medical statistics, research, and breast cancer treatment. You can find a list of the members of the breast screening review panel on this link.
The benefit of breast screening is that some women will have a breast cancer found at the earliest possible stage, before it has caused any symptoms.
Many cancers found during screening would have been found later if women hadn’t been screened. Some will be successfully treated and others unfortunately won’t. But the screening programme does mean that more cancers are successfully treated than if we didn’t have screening.
The possible harms from breast screening are
- Diagnosing slow growing breast cancers that would never have caused any harm (overdiagnosis)
- Exposure to small amounts of radiation during screening
- Unnecessary anxiety in women who are called back for more tests, but found not to have breast cancer
Overdiagnosis was the main issue that the Panel considered and is a major problem. Some breast cancers found through screening would never have become life threatening. But currently doctors can’t reliably tell whether a breast cancer found during screening is life threatening or not. So women who have breast cancers found through the screening programme are all offered treatment. This is why we talk about ‘overdiagnosis’ – these women go on to have cancer treatment that they would never have needed had they not been screened. And of course they have the side effects and anxiety that anyone having treatment for cancer goes through. One of the main aims of the screening review panel was to try to find out how many women are overdiagnosed.
Any risk from radiation from mammograms is likely to be very small. For every 10,000 women who have regular 3 yearly screening between the ages of 47 and 73, experts estimate that there will be between 3 and 6 extra breast cancers caused by radiation.
In the screening programme, there are far more women called back for tests who turn out to be fine than who actually have breast cancer. Only about 1 in 25 women are called back and about 1 in 5 of those will have breast cancer. So, 4 out of 5 women called back don’t have breast cancer. Of course, when they are called back, these women will be very anxious that they do have cancer.
The panel looked at all the existing research on breast screening that was relevant to the UK Breast Screening Programme. This included randomised controlled trials and observational studies.
A randomised trial puts people into groups at random and, for example, half are screened and half not. The researchers then follow the groups to see what happens to them.
An observational study collects data on what happens to people who either take part in screening or don’t. They may have made the choice themselves. Or screening is either on offer or it isn’t (because they live in countries that have different policies, for example).
All the randomised trials were set up at least 20 to 30 years ago. The observational studies were more recent.
It is important to put the findings in context with the breast screening programme as a whole. In the year from April 2009 to March 2010, 1,998,225 women between 50 and 70 had breast screening in the UK and 15,517 of these women had cancer diagnosed.
The Panel found that overall in the UK, having a breast screening programme means that about 1,300 breast cancer deaths are prevented each year. These are cancers that are found and treated earlier than they would have been if we didn’t have a screening programme.
But also, out of the total of around 15,500 women diagnosed with breast cancer through screening, 4,000 of them are overdiagnosed. So around 1 in 4 of women diagnosed with breast cancer through screening would never have had a problem from their breast cancer if they hadn’t been screened.
The Panel say that there is little reliable research evidence on how many women are diagnosed with breast cancers that would not go on to cause them any problems (an overdiagnosed breast cancer) so this is the best estimate they could produce given the lack of reliable evidence.
To simplify the figures as much as possible, for every breast cancer death prevented through screening, about 3 women will have treatment for a cancer that would not have caused them problems. Their doctor would not have known that at the time because they can’t reliably tell which breast cancers are life threatening and which aren’t.
Do remember, these are the best estimates that the Panel could produce, given the lack of reliable evidence available about the extent of overdiagnosis. And remember, this is 4,000 overdiagnosed each year out of a total of 15,500 breast cancers diagnosed through screening.
Thinking about the benefit to the country as a whole, the Panel’s conclusion is that the UK breast screening programmes has significant benefit and should continue.
The decision for any individual woman is not necessarily an easy one. That is why we have tried to set out the evidence as clearly as we can. There are two sides to it and only you can decide which is more important to you. Cancer Research UK has worked out the following statistics to try to show the benefits and risks as clearly as we can.
After 20 years, out of 1,000 women who have screening, 75 will be diagnosed with breast cancer and have treatment. Out of these 75 women
- 16 will die from breast cancer
- 59 will be successfully treated and survive their breast cancer
Whereas, after 20 years, amongst 1,000 women who have not had screening, 58 will be diagnosed with breast cancer. Of these 58 women
- 21 will die from breast cancer
- 37 will be successfully treated and survive their breast cancer
So for every 1,000 women screened there are 5 lives saved at the expense of 17 women being diagnosed and treated for a cancer that would never have caused them any problem.
You can’t know whether you will benefit from screening or end up having treatment that you might never have needed. If you choose to be screened, you are accepting the chance of having your life extended, but also risking being overdiagnosed and having at least a lumpectomy or mastectomy, and possibly other cancer treatment. If you choose not to have screening, you run a slightly higher risk of dying because a breast cancer wasn’t found early enough.
On balance, taking all the evidence into account, Cancer Research UK recommends that women go for breast screening when invited. There is a link below to our full statement.
If you would like to talk this through with someone, you can contact our cancer information nurse team.
We’ve also produced
- A short video about the review and its implications (this will open in a new window)
- A detailed diagram (infographic) that sets out the numbers in a different way (this will open in a new window)
- A blog post about ongoing research to improve breast screening
- The breast screening review panel’s press release
- An official statement on the review from Cancer Research UK
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