Two months ago, I read on the BMJ website Citizens jury disagrees over whether screening leaflet should put reassurance before accuracy.”
I asked Angela Coulter, PhD, to write a guest blog post about the matter. She is a member of the Expert Panel on Invitation Support Materials for NHS Cancer Screening and she acted as an expert witness during the citizens jury. She is also director of Global Initiatives for the Informed Medical Decisions Foundation, which supports HealthNewsReview.org.
Here is her guest post.
Breast screening has long been controversial among epidemiologists, but most women are unaware of doubts about its effectiveness. The UKs NHS breast screening programme, which has been in operation since 1988, invites all women between the ages of 50 and 70 to undergo a mammogram every three years. The current invitation letters and accompanying leaflets have been heavily criticised for failing to mention potential harms of breast screening, in particular the risk of overdiagnosis and overtreatment (http://www.bmj.com/content/338/bmj.b86).
In response to this criticism, Sir Michael Richards, National Cancer Director for the NHS, asked eminent epidemiologist Sir Michael Marmot to chair an independent committee to review the evidence on benefits and harms of breast screening and make recommendations on what women should be told. The Marmot report , published in the Lancet (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2812%2961611-0/abstract), concluded that screening prevents about 1,300 breast cancer deaths a year in the UK, but results in about 4,000 women undergoing treatment for a condition that would never have troubled them.
Redesign of the breast screening invitation letters and leaflets is now under way. This work has involved wide public consultation and a specially convened citizens jury (http://www.bmj.com/content/345/bmj.e8047). The jurors were 25 randomly recruited women aged between 47 and 73 who met in London to hear evidence from experts and make recommendations on the best way to present Marmots conclusions to women. They embraced the unfamiliar task with great enthusiasm and commitment. After three days listening to nine expert witnesses and deliberating amongst themselves, jurors concluded that the leaflet must explain DCIS, with numbers showing what proportion of screen-detected cancers it represents and the consequences of a positive result. They recommended the use of side-by-side icon arrays to show the benefits and harms of screening, and they made the following recommendations on language and numbers: use numbers of lives saved per year rather than life years saved; overtreatment not overdiagnosis; those attending screening rather than those invited as the denominator; and the need to explain the uncertainty around the various estimates.
Jurors were asked for their views on the process and their responses were overwhelmingly positive. One participant remarked: I cant believe how much I didnt know.
A full report of the consultation, including videos of the citizens jury, can be found at http://www.informedchoiceaboutcancerscreening.org/.
PUBLISHER ADDENDUM ON JANUARY 23: The BMJ sent out this news release today.
Michael Baum, Professor emeritus of surgery at University College London says that, while deaths from breast cancer may be avoided, any benefit will be more than outweighed by deaths due to the long term adverse effects of treatment.
He estimates that, for every 10,000 women invited for screening, three to four breast cancer deaths are avoided at the cost of 2.72 to 9.25 deaths from the long term toxicity of radiotherapy.
These figures contrast with an independent report on breast cancer screening, led by Sir Michael Marmot and published in November last year. Marmot and his committee were charged with asking whether the screening programme should continue, and if so, what women should be told about the risks of overdiagnosis.
They concluded that screening should continue because it prevented 43 deaths from breast cancer for every 10,000 women invited for screening.
The downside was an estimated 19% rate of overdiagnosis: 129 of the 681 cancers detected in those 10,000 women would have done them no harm during their lifetime. However, those women would have undergone unnecessary treatment, including surgery, radiotherapy and chemotherapy.
But despite this higher than previous estimate of overdiagnosis, they concluded that the breast screening programme should continue.
The report also judged that screening reduces the risk of dying from breast cancer by 20%. But Professor Baum disputes these figures, saying the analysis takes no account of improvements in treatment since these trials were done, which will reduce the benefits of screening. Nor does it make use of more recent observational data.
With these data included, estimated rates of overdiagnosis as a result of screening increase to up to 50%, he argues.
This is important because it can change the decisions women make when invited for screening. In a study also published today, researchers at the University of Sydney explored attitudes to screening in a sample of 50 women. Many of the women were surprised when they were told about overdiagnosis and most said they would attend screening if overdiagnosis rates were 30% or lower, but a rate of 50% made most of them reconsider.
An accompanying editorial points out that the harms of screening will reduce as more effective diagnostic processes develop to inform less harmful and more personalised treatments. In the meantime, it says women need up to date and transparent information about the benefits and harms of screening to help them make informed choices.
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