BMJ editorial questions the effectiveness of mammography

Perhaps more than any other disease, breast cancer has received a helluva lot of social and political attention over the last decade. And a big part of the trust around raising awareness of the disease is the ‘need’ for women to be screened for breast cancer. The most commonly used technique for this is mammography ” essentially and x-ray of the breast. The idea here is that earlier detection though mammography and more timely treatment will reduce the likelihood that a woman will succumb to breast cancer.

While this makes sense, we now seem to have a enough data to make a decent assessment at just how effective mammography is in terms of saving lives. A round-up of the available science was presently earlier this month in a British Medical Journal editorial. I think the data makes for some interesting reading.

The data presented shows that in women aged 50-69, about 9 in every thousand will be expected to die from breast cancer over a 10-year period if the population is NOT screened with mammography. However, if screening is applied to that population, the number of women expected to die falls to 6 per 1000. Thus, mammography appears reduce risk of death of breast cancer over a 10-year period by a third.

This looks good, but it’s perhaps important to bear in mind that, in real terms, this means screening causes risk of dying from breast cancer over a 10-year period from about 0.9 % to 0.6 % – a reduction in risk of just 0.3 %.

The figures for younger women are even less impressive. Mammography appears to cause deaths in women aged 40-49 to drop (again, over a 10 year period) from 3.3 to 2.5 per thousand. This translates into a real risk reduction of 0.08 per cent. Put another way, for each 1000 women aged 40-49 who undergo mammography, less than 1 life will be saved as a result of this procedure.

In addition, one thing that is sometimes forgotten about mammography is that it is far from foolproof. There is the risk, of what are known as ‘false positive’ results. Essentially, this means results that are suspicious of cancer that turn out not to be cancer but nonetheless require a woman to go through further testing and investigation. The editorial in the BMJ reckons that for every 1000 women screened, 100 – 500 (10 ” 50 %) will end up with a false positive result.

And there’s one other thing. Even in women diagnosed with real breast cancer, the treatment the end up having may in fact be ‘unnecessary’. This may seem counterintuitive on first reading, but hear me out. Imagine a woman develops breast cancer but dies of something else before that cancer is diagnosed. Now imagine this women is screened, has her cancer diagnosed, and then is treated. In reality, this treatment has not helped her because she was not destined to die from breast cancer anyway. However, she may still have had potentially disfiguring surgery, as well as radiotherapy and/or chemotherapy.

The problem, of course, is that when breast cancer is diagnosed, doctors are fresh out of crystal balls and cannot tell for whom treatment will be relevant. This means that more-or-less everyone gets treated. And that means, whether we like it or not, that some women will be treated unnecessarily.

The BMJ editorial also presented data on women who appear to have had an unnecessary diagnosis and treatment for breast cancer.� In women aged 40-49 it is 2-5 women per 1000 (you might want to compared that to the less than 1 life that is saved through mammography). In women aged 50-69, it rises to 3-9 per 1000.

My experience is that mammography is generally touted as a ‘must’ for women of a certain age, but its potential downsides (including the risk of unnecessary diagnosis and treatment) rarely get an airing. The authors of the BMJ editorial make this point, and go on to suggest that women should not be told what to do with regard to mammography, but be encouraged to make a decision that is right for them.� What this means, inevitably, is giving women the best data we have on both the benefits and pitfalls of mammography. That way, they can make a truly informed choice about whether to undergo this test.

References:

Schwartz LM, et al. Participation in mammography screening. BMJ. 2007 13;335(7623):731-2.

11 Responses to BMJ editorial questions the effectiveness of mammography

  1. Sue 24 October 2007 at 8:18 am #

    I think I read somewhere that mammograms can increase the spread of the tumor. Because of the way the breast has to be compressed the tumor (if there is one) may also be compressed and cause the tumor to rupture and spread!
    Correct me if I’m wrong.

  2. Dr John Briffa 24 October 2007 at 8:42 am #

    Sue, don’t know anything about this, but I had a look on-line and found this:
    http://www.preventcancer.com/patients/mammography/dangers.htm

  3. Kate 25 October 2007 at 10:58 am #

    Perhaps it’s time to seriously look into alternatives to mammograms?
    It is very painful and unpleasant and feels almost like a punishment for having breasts. Just imagine if that was the way to screen for testicular cancer – how long would that have lasted?
    hmmmm….about 5 minutes?

  4. chris 25 October 2007 at 4:42 pm #

    I think that there is a new way of xraying that will be introduced – i have read something but cannot remember where.
    I had a scare a few years ago and have to say having a mammogram was a tiny bit uncomfortable but lasted a few seconds. I think they are reassuring – having seen many women over the years who have been saved by them I would always take up the offer. Just imagine not taking the test and there is a lump there!

  5. Sue 26 October 2007 at 3:04 pm #

    Another form of screening is Thermography which is totally non-invasive and can detect abnormalities in the breast years before a mammogram. The results also have a higher percentage of accuracy. Why this has not been adopted as a screening method amazes me. It is available in the US on a large scale compared with only a handful of private clinics in the UK. I had mine done at The Chiron Clinic in Harley Street followed by a consultation with Dr Nyjon Eccles. I found the whole procedure pleasant and reassuring and have since recommended thermography to my patients.

  6. carole 27 October 2007 at 10:46 am #

    Because my mother died of breast cancer I was under the family history clinic. The whole idea that I will get breast cancer because my mother did makes no sense. I have changed my behaviour, my diet and have already lived 10 years longer than her. I have therefore left the family history clinic and feel better for it.(not having mammogram is a blessing too) I no longer focus on the negative I focus on the positive things I have from my mother. How about we start talking to people about being positive and cheerful rather than asking them to focus on the negative things in their family?

  7. chris 28 October 2007 at 3:00 pm #

    well I am sure alot of people couldnt afford it – so your clients are very lucky. I didnt wait either because I have bupa cover but some have to wait weeks.

  8. helen 28 October 2007 at 9:28 pm #

    Carole you are so right – “Because my mother died of breast cancer I was under the family history clinic. The whole idea that I will get breast cancer because my mother did makes no sense.” We are actually paying for OUR problems to be diagnosed & treated not our family’s illnesses. Personally I never indicate that there is a history of anything in my family because I want my problem if I have one treated not my mothers or fathers or great aunt’s. ]
    Kate you are also correct if men had to subject delicate parts of their anatomy to such horrific barbaric torture like “intervention” a better way would be found instantly. I personally think early detection is a false promise anyway by the time you take the treatment which is often worse than living with the cancer you have not extended your life span by one day in fact taking the chemical route to cancer treatment is a bit like drinking draino to cure a bowel blockage, keeps the chemical (drug) company in the money but does absolutely nothing for your quality of life.

  9. chris 29 October 2007 at 8:37 am #

    mm – i have read this twice are you saying you wouldnt have any treatment- please explain or am I reading this incorrectly.

  10. Hilda 3 November 2007 at 4:55 pm #

    Prevention has to focus on getting the right fats into the cell membrane so that hormones can lock on properly to receptors. THis means not eating any processed oils (not just hyd oil except olive oil) as the cell membrane is made up of lipids. Veg oils are absolutely everywhere and in everything (raisins are often coated in it). We need to educate the publc about this

  11. Josephine 1 July 2009 at 10:52 am #

    Aged 39. Advised by GP to have a mamogram (mother died of breast cancer). Had heard that they weren’t that effective, but had come to accept that it was a regular preventative and routine procedure from ‘a certain age’. What I had NEVER heard was that it was so desparately painful. I would go so far as to say torture. I came away feeling that I could never go through that again. That the procedure had done more harm that good. That this very delicate part of my body would take weeks to recover. Do people keep this quiet so as not to put women off? Well, I’m put off now.

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