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Are women being misled about pros and cons of breast screening?

In the second of our occasional series of short essays, Dr Margaret McCartney argues that women deserve better information about the risks as well as the benefits of breast screening - and questions whether the programme is cost-effective

In the second of our occasional series of short essays, Dr Margaret McCartney argues that women deserve better information about the risks as well as the benefits of breast screening - and questions whether the programme is cost-effective

Over the past couple of decades the medical profession has had its paternalism stripped away. These days we could drown in information downloaded from the internet, and sharing healthcare experiences and medical knowledge is commonplace. Yet there are still enormous gaps in some kinds of healthcare information. One of those gaps is in the information women currently get about breast screening.

The debate about what information is needed for consent to screening to be informed was recently reignited by a letter, which I co-signed, to The Times. I and my co-signatories called for better information about breast screening to be provided to women. Our letter was submitted in response to a paper in the BMJ by Dr Peter Gotzsche and colleagues, which observed there had been no great improvements in the information women were getting1.

Dr Gotzsche, who is the director of the Nordic Cochrane Centre, had previously performed reviews on the effectiveness of breast screening.

The good news is that the NHS Breast Screening Programme says that it is going to 'rip up' the current leaflets that are given to women and start afresh. This sounds good, but I am concerned the rethink will not go deep enough.

Pros and cons

Primarily, it has to be made clear that breast screening is a choice and not a compulsion. Rather than encouraging women to come for screening, do we not have to explain the pros and cons and let each woman decide?

I asked Julietta Patnick, director of the NHS Cancer Screening Programmes, about this earlier this year. Questioned whether women were truly given a choice over breast screening, she said breast screening was a choice - but that she wanted women to choose to have it.

This doesn't sound like a free choice to me, but rather one that is directed to what the health service considers the right outcome. But then the NHS Breast Screening Programme has a vested interest. It has to get people to turn up for screening. So is the programme best placed to write unbiased information leaflets about what it offers?

It is essential to give women fair information, because breast screening has a lot of cons as well as pros. The most recent systematic reviews2,3 of its effects found that if 2,000 women were screened regularly for 10 years, one woman would avoid dying of breast cancer. However, 10 other healthy women would be treated for breast cancer found at screening - but would not benefit from the treatment, as they were never going to die from it.

And out of the 2,000 women who are screened, 200 will have a 'false alarm' and be recalled for more tests, before they are told they don't have breast cancer. This can, of course, cause distress and alarm.

To some women the benefits of screening will seem fairly marginal. To others, it will seem well worth the potential risks. Just like any other medical procedure, doctors have a duty to explain the risks and side-effects of screening as well as its benefits.

Cautious approach

There are real problems with breast screening that merit a cautious approach to it. First, there is 'overdiagnosis' or what is sometimes called 'pseudodisease'. It is not just definite cancer that gets detected at breast screening. There are other abnormal lesions where the prognosis is far from certain, such as ductal carcinoma in situ, which comprises about 20% of 'breast cancer' diagnosed at screening in the UK.

These are commonly treated with surgery - often mastectomy - and possibly also chemotherapy and radiotherapy. But only a minority (the exact percentage is disputed) may have ended up progressing to a life-threatening cancer. In other words, for many of these women, the medical interventions that are offered were never going to help because the cancer was not going to progress in an aggressive, life-threatening way.

Studies done at post-mortem suggest that between 15% and 39% of women die with, rather than from, this type of cancer. This draws a parallel with some cases of prostate cancer, which are diagnosed by screening but which are similarly co-existent.

There are other disadvantages too. It is important not to overplay the risks of radiation via mammography, but the risks do exist. The NHS Breast Screening Programme says, in publication number 61 of 20064, that 'for every 14,000 women in the age range 50 to 70 screened by the programme three times over a 10-year period, the associated exposure to X-rays will induce about one fatal breast cancer'.

As the potential gains of breast screening have fallen, because of improvements in treatment and through less dangerous cancers being detected, the potential side-effects become more important.

This leads me to ask: is breast screening really cost-effective enough to merit running a programme at all? Rightly, NICE and the Scottish Medicines Consortium are interested in working out the cost-effectiveness of interventions and using the ones that are thought to be justified. But breast screening started in 1988 after the Forrest Report recommended it two years earlier, and has not undergone appraisal by NICE or the SCM. We might get more quality-adjusted life-years for our buck if we spent them on, for example, treatments for non-screen diagnosed breast cancer, or indeed other diseases.

But although I would support a full cost-effectiveness review, this is likely to take some time. Meanwhile, women need better information about the risks and benefits. It may be useful to refer our patients to for statistics on the risks and benefits of breast screening that are evidence-based.

Dr Margaret McCartney is a GP in Glasgow with an interest in evidence-based medicine - she writes a column for the FT Weekend as well as a blog

Is breast screening really cost-effective enough to merit running a programme at all?

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