The Breast screening review is out

New things today 31/10/12

Article in Pulse (free reg needed) 

Comment is free in the Guardian

Here is the press release from the Lancet:

Independent panel concludes that breast cancer screening reduces deaths, but overdiagnoses

**Embargo: 00:01 [UK time], Tuesday October 30, 2012**

An independent panel of experts has concluded that routine breast cancer screening results in a reduced risk of dying from breast cancer compared to when no screening takes place, but that screening also results in overdiagnosis, according to a Review published in The Lancet.

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 overdiagnosis – 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 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%.

Despite a scarcity of reliable studies on overdiagnosis (there were only three randomised trials available), the Panel concluded that for the roughly 307 000 women aged 50-52 years who are invited to begin screening every year, just over 1% will have an overdiagnosed cancer in the next 20 years.

Putting together benefit and overdiagnosis from the above figures, the Panel estimate 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 overdiagnosis, and 43 deaths from breast cancer will be prevented.

However, given the uncertainties around all of these estimates, the Panel state that the figures quoted give a spurious impression of accuracy, and further research will be needed to more accurately assess the benefits and harms of breast cancer screening.

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 3 years, probably prevent around 1300 breast cancer deaths every year.  However, our estimates also suggest that each year around 4000 women are overdiagnosed as a result of screening.”*

“For each woman, the choice is clear.  On the positive side, screening confers a reduction in the risk of mortality of breast cancer because of early detection and treatment.  On the negative side, is the knowledge that she has perhaps a 1% chance of having a cancer diagnosed and treated that would never have caused problems if she had not been screened.  Clear communication of these harms and benefits to women is essential, and the core of how a modern health system should function.”*

A Lancet Editorial, published alongside the Review, concludes that “The Panel’s report, the latest and best available systematic review, shows that the UK breast-screening programme extends lives and that, overall, the benefits outweigh the harms. Dissemination of these findings is now imperative in the media, the NHS screening programme, and between doctors and their patients. Women need to have full and complete access to this latest evidence in order to make an informed choice about breast cancer screening.”

 

For full Review, see: http://press.thelancet.com/breastcancerscreeningreview.pdf

For Lancet Editorial, see: http://press.thelancet.com/breastcancerscreeningeditorial.pdf

 

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)61611-0/abstract

Points;

1) They did not look at all cause mortality, but breast cancer deaths. Yet all cause mortality is very important in screening interventions, see here http://jnci.oxfordjournals.org/content/94/3/167.longY

2) This was not a systematic review.

3) The trials analysed are 20years old. Breast cancer treatment has improved hugely since then. The advantage of finding some tumours earlier may now be outweighed by the fact that treatment is so good.

4) Cancer Research UK have said in the press conference http://press.thelancet.com/breastcancerscreening.mp3 that they will continue to ‘recommend’ that women attend screening.

Sorry, but this is simply wrong. It is paternalistic. CRUK are making a value judgement that they feel it is worth being treated needlessly for breast cancer (overdiagnosis) because there is also a chance that screening might stop your death from breast cancer.

This is unfair. It is not up to them, it is up to the woman in question.

This is what the recommendations say, and it’s important to remember that they have also said “the Panel state that the figures quoted give a spurious impression of accuracy” but estimate then ” 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 overdiagnosis, and 43 deaths from breast cancer will be prevented.”

We are no longer in the realm of paternalistic medical decision making, but the irony here is that it’s a charity that’s making a value judgement for you. It is only in screening that we intervene with the potential to do so much harm in an asymptomatic person, and where we do not give people properly informed consent first. Medicine has been at fault in failing to explain the pros and cons of screening from the start; it has never been straightforwardly beneficial.

I await the findings of Informed Choice in Cancer Screening.

 

 

 

 

 

 

 

9 Responses to “The Breast screening review is out”

  1. Dr Mills October 30, 2012 at 7:49 am #

    CRUK has always liked intervention particularly with expensive drugs

  2. steve October 30, 2012 at 8:49 am #

    “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 3 years, probably prevent around 1300 breast cancer deaths every year. However, our estimates also suggest that each year around 4000 women are overdiagnosed as a result of screening.”*

    Now correct me if I am wrong here BUT what this actually says is that if you have breast screening you have a 1 in 180 chance of benefit (i.e. a 0.55% chance of benefit) and a 179 in 180 (i.e. 99.45%) chance of no benefit. In addition you are 3x more likely to be harmed by the screening process than you are to benefit from it.

    In addition Margaret your point about overall mortality is well made because ultimately that’s what matters with any cancer screening – we don’t just want fewer people to die from that cancer we want them to live longer as well otherwise there is little point if they just live the same length of time and die of something else instead. Or am I being a tad too cynical?

  3. Michael Power October 30, 2012 at 11:29 am #

    Thanks Margaret for an incisive critical appraisal of the Marmot Report and the CRUK response.

    Risk is so hard to understand and communicate that often concomitant uncertainties, ambiguities, and ignorance are ignored. This is what CRUK seem to have done. I hope that the King’s Fund “Informed Choice in Cancer Screening” project did not set themselves the same trap – their questionnaire was so focussed on understanding and communicating risk that I will be surprised if their forthcoming report does not underplay the other uncertainties, like old data, newer treatments, unmeasured outcomes, and personal preferences for style of being given information and recommendations.

  4. Maya October 30, 2012 at 1:03 pm #

    Would you know please what % of cancers diagnosed each year in the UK are as a result of screening and what % is as a result of women being asked to be referred to a specialist due to others symptoms such as a lump or other changes in the breast?

  5. steve October 30, 2012 at 5:02 pm #

    Good question Maya for which I don’t have an answer.
    Another question is how much of the decline in breast cancer since screening was introduced is down to screening (as opposed to say better surgery, better drug therapy, etc.).
    The rate of breast cancer in the UK peaked in 1986 at 41.7 cases per 100,000 women per annum (i.e. 0.042%). Screening was introduced two years later but only achieved national coverage in the mid-1990s by which time annual incidence had fallen to 37 per 100,000 (i.e 0.037%). The figure now stands at 24.4 per 100, 000 (i.e. 0.024%) – a relative reduction since screening began of nearly 50% but an actual reduction in the annual incidence of 0.016%.

  6. steve October 30, 2012 at 10:10 pm #

    Oops – above post refers to rate of breast cancer deaths – sorry!

  7. EEB November 3, 2012 at 1:57 am #

    I don’t accept the figure for lives saved by screening, I’ll stick with the information from the Nordic Cochrane Institute, that is….screening is of little benefit and leads to significant over-diagnosis. I practice breast awareness. (no mammograms, clinical breast or self exams) Vested and political interests run deep in women’s cancer screening, high emotion and no respect for informed consent…some women just receive their invitation in the mail complete with date and time. I have never approved of the assumption that women will just do as they’re told…and have always hated the impatience from all quarters with those women who choose not to screen and the name-calling, we all have a right to say no to cancer screening….the coercive and paternalistic nature of women’s cancer screening needs to change and that means every woman needs to reject the orders, challenge misinformation and push for change….less emphasis on targets and more on the individual and informed consent and an acceptance that some women will choose not to screen. Like Dr McCartney, I have also declined pap tests as well. It was wonderful to see a doctor brave enough to admit that fact, isn’t it incredible that most women are afraid to admit they don’t have or don’t want cancer screening? It shows something is not right in women’s cancer screening.

  8. Cameron November 28, 2012 at 4:13 pm #

    Hi,

    I have a quick question about your blog, would you mind emailing me when you get a chance?

    Thanks,

    Cameron

  9. Deborah Cross August 3, 2013 at 7:11 pm #

    “… for 10,000 women invited for screening from age 50 for 20 years it is estimated that 681 cancers (invasive and DCIS) will be diagnosed of which 129 will represent overdiagnosis (using the 19% estimate of overdiagnosis) and 43 deaths from breast cancer will be prevented”. I will use these figures and others from the review, whilst accepting that the precision is spurious.

    Using the figure of 20% for reduction in breast cancer mortality in the previous paragraph of the review, I assume that the remaining 80% (43×80/20) = 172 of the 681 women will still die from breast cancer; that is 25% of those 681 diagnosed with cancer.

    What about the remaining 681-129 -43 -172=337? All I can think is that they don’t die from breast cancer, and wouldn’t have even if they hadn’t been screened, presumably as a result of treatment they would have had when they presented to a doctor at a later date. Do people agree? I saw no statistics showing whether these 337 women had less extensive interventions as a result of screening.

    Thought experiment with the 681 women: Assume the screening is completely covert (yes, I know that’s impossible, which is why it is a thought experiment) and the women are not told the results, so their behaviour is not influenced by screening. I assume 43+172=215 will die from breast cancer (32%). The remaining (681-215=) 466 won’t die from breast cancer, either because they will never know that they had cancerous tissue (the 129 who would have been called ‘over-diagnosed’) or their cancers were diagnosed by other means and treated successfully (the 337 above).

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