This morning there are many women across Britain, not to mention a few charities, who will have woken up to what seems to be some very reassuring news:

Breast cancer screening does ‘more good than harm’

Breast cancer screening does more good than harm, with any over-treatment justified by the number of lives saved, say experts.

Mammograms can spot dangerous tumours, but might also detect lumps that are essentially harmless, exposing some women to undue anxiety and surgery.

But data suggests screening saves the lives of two women for every one who receives unnecessary treatment.

Even allowing for the generally abysmal state of science/medical journalism, as practised by mainstream news organisations, this is a story that I find particularly frustrating.

Its not that there’s anything particular wrong with the core content of the story. In fact, the coverage given to the newly published research on which the story is based is actually pretty good. The information given in the story is presented clearly and, for once, the report uses absolute rather than relative statistics, which give a far more accurate picture of the findings that are being reported.

And yet, for all that, the report itself is still pretty misleading and not because of what it does say, but because of the what it doesn’t.

What the BBC doesn’t say.

The heart of the problem lies squarely in this statement:

Previous research has cast doubt on the benefits of screening women for breast cancer, and it is a debate that is ongoing among experts.

This is perfectly true but omits a very important detail – most of the research that has cast doubts on the value of breast cancer screening, and the ongoing debate amongst ‘experts’ relates to the benefits and drawbacks of offering routine screening to younger women, i.e. women under fifty, where the evidence for the benefits of screening is much more equivocal that it is for older women.

The best way to explain the issue here is to look at the figures – these are from the study that the BBC is currently reporting and are derived from an analysis of the UK’s screening programme under which all women aged between 50 and 70 are offered a mammogram every three years:

The research, by experts from the Wolfson Institute of Preventive Medicine at Barts and the London School of Medicine and Dentistry, estimated that 5.7 breast cancer deaths were prevented for every 1,000 women screened over a 20-year period.

At the same time, 2.3 women per 1,000 were told they had a lump but it was not clear if it was an aggressive form of cancer that needed to be treated.

Put another way, for every 28 cases diagnosed, 2.5 lives were saved and one case was over-diagnosed.

For women in their forties, however, the picture looks very different.

As far as the impact of screening on mortality is concerned, evidence from 280,000 women included in four studies conducted in Sweden in the 1990′s found that routine screening of women in their forties reduced the breast cancer mortality rate in that age group from four in 1,000 to three in 1,000, preventing one breast cancer death for every 1,000 women screened.

As for the risk of over-diagnosis, the false positive rate for mammography can vary considerably from country to country depending on how the results of the test are evaluated – the Netherlands has, for example, one of the lowest false positive rates of any country at just 1% while the US has the highest false positive rate in the world at up to 15%. In the US, 15 out of every 100 women diagnosed with breast cancer on the basis of a mammogram will subsequently be found to have had a false and matter are further confused by the fact that mammograms will also uncover a significant number of cases of an non-invasive form of breast cancer called Ductal Carcinaoma in Situ (DCS) only one in five of which will develop into an invasive and potentially life-threatening cancer over time.

As a result, anything up to 9 out of every 1o women in the forties screened in the US may be overdiagnosed and undergo further invasive medical procedures. At the very least this means a biopsy, i.e. the removal of breast tissue for further tests, although so will opt immediately for a full or partial mastectomy.

For an American woman who begins annual screening aged 40, the chance of having at least one false positive before the age of 50 can be as high as 1 in 2.

Understandably, therefore, some doctors have started to question the value of providing routine breast cancer screening to women under 50, where those women present without any relevant symptoms and lack the kind of personal or family history of cancer which suggest that their risk of developing breast cancer is much higher than normal. These same doctors have also raised a number of important ethical questions in regards to the information that women are given about screening, much of which has, to date, failed to address the issue of over-diagnosis.

The issue here is one of weighing the physical, emotional and financial costs of over-diagnosis against the benefits of screening and the risks of a false negative, a case in which a woman does have an invasive breast cancer that is missed during screening, which can occur in up to 1 in 1000 cases. As a consequence of over-diagnosis around 70 in 1000 women screened from breast cancer in their forties, in the US, will unnecessarily undergo an invasive and disfiguring medical procedure and have to cope with the emotional stress and anxiety of having been diagnosed with breast cancer in order to save one life. The financial cost to the US healthcare system is also significant – mammography screening costs around $2100 per woman per year and the on costs associated with follow-up tests and treatments arising out of over-diagnosis are estimated to cost the US system something of the order of $100 million a year.

The good news, for American doctors, it that its rare that a woman who is misdiagnosed as having breast cancer after routine screening will sue for malpractice – the vast majority are simply too relieved on being given the all clear, after a biopsy, to even consider litigation as an option. On the other hand, the relatively rare cases in which a false negative is recorded and an invasive cancer is missed will invariably result in a malpractice suit, prompting a safety-first approach to diagnosis, which goes some considerable way towards explaining why the over-diagnosis rate in the US is so much higher that it is other countries where women in the forties are also screened as matter of routine.

So how big an issue is this?

This is not a major issue in the UK – yet.

Our own screening program, as the study being reported today shows, operates in a manner in which the risk of over-diagnosis is minimised relative to overall benefits of mass screening. This could, however, change in the future should the government of the day decide to extend the scope of the NHS screening programme much beyond its current plans, which will soon see routine screening offered to women aged between 47 and 73. A future government may even come under pressure to extend the UK’s screening programme further and all the more so if private healthcare providers are given significantly greater scope to compete for NHS-funded services, for reasons that should be apparent if we consider what’s been happening in the US over the last few months.

Breast cancer screening has been one of the hot issues in the US over the last few months following the publication of revised guidance on the conduct of screening programmes by the US Preventive Services Task Force. In November, the USPTF updated its advice on mammography screening to take in account the new evidence on its effectiveness and came out against the routine screening of asymptomatic women in their forties  – it had previously recommended that these women should undergo screening once every two years. These new guidelines also recommended that women over the age of 50 should be screened every two year, rather than ever year as was previously the case.

This has had the effect of formally reducing the grade given for evidence quality for the screening of women in the forties from grade B to grade C, prompting strong opposition from cancer advocacy groups and, inevitably, doctors. It also, for a time, made these new guideline something of a hot political issue during the recent ‘Obamacare’ debate.

Under the recently passed US healthcare reform package, health insurance companies are required, by law, to cover the costs of screening programmes and other preventative services rated at grades A and B for evidence quality but are given discretion over whether or not to cover services given a lower grade.

In response to the USPTF’s new recommendations the US senate, in December last year, passes an amendment introduced by a Republican Senator, David Vitter, which formally set them aside. Vitter – it should be noted – has so far received close to $400,000 in campaign contributions from healthcare professionals in support of his run for re-election to the Senate later this year, more than has been donated to his campaign by any other single industry sector; although he naturally claimed that his amendment was prompted by concern for women’s health rather than his campaign war chest.

What this illustrates, more than anything, is one of the major flaws than can arise in the kind of consumer-driven, insurance-based, healthcare systems favoured by some on the right.

America has, on paper and by some distance, the best preventative healthcare system in the world. It is also, by far, the most costly system in the world and one that performs somewhat less well than the NHS on a number of key metrics, including average life expectancy and mortality/morbidity from preventable lifestyle related conditions, i.e. those linked to obesity, smoking, alcohol consumption. etc. Much of the phenomenal cost of of the current US system, which consumes getting on for twice the amount of money, as a proportion of GDP, than any other comparable healthcare system in the world, stems from the costs of its preventative healthcare services, some of which deliver only marginal benefits at the expense of excessive spending on mass screening programmes and on unnecessary and, often, disfiguring medical procedures.

This is problem that the UK’s evidence-based approach to screening successfully avoids, at least for the time being, but one that could easily be compromised in future if too much credence is given by policy-makers to consumer choice in healthcare at the expense of scientific evidence; a facet of our own debate around healthcare reform that has, to date, received far too little attention.

Reader comments

1. Jay Adams

   Liberal Conspiracy » What the Beeb didn't say about breast cancer … http://bit.ly/aZvHPf

2. Unity

   RT @libcon: What the Beeb didn't say about breast cancer screening http://bit.ly/a3Oz1W

3. Thetis

   excellent post from Unity RT @Unity_MoT RT @libcon: What the Beeb didn't say about breast cancer screening http://bit.ly/a3Oz1W

4. Liberal Conspiracy » Why the Tory party’s promise on cancer-screening is empty

   [...] already has a long established breast cancer screening programme which, as I pointed out only recently, the UK’s existing screening programme is about as optimal as its possible to get given the [...]

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