I am against over-medicalisation in all its forms. So, apart from being very skeptical about preventative medicine in the area of heart disease, I also worry about other forms of preventative medicine. Breast cancer screening is one area where the balance between benefit and harm may well slip towards harm. Yet, it is presented as an absolute good.
One man who is very critical of breast cancer screening is Professor Peter Gotzsche, who is the clinical director fo the Nordic Cochrane Collaboration Centre, and has written a book called ‘Mammography Screening. Truth, lies and controversy.’ He outlines exactly what has been going on in this are, and makes it very clear that there are significant problems. Primarily with overdiagnosis (there are other problems, but no time for everything in one blog).
Overdiagnosis means finding ‘lumps’ of other suspcious things on mammography ‘lumps’ that would never have caused any problem. How big is this problem. Well, detailed pathological studies done in Australia found that in women who had died of other thngs (not breast cancer) had the following pathologies, any of which could lead to a ‘diagnosis’ of breast cancer if found on a biopsy :
|Carcinoma in situe||13%|
|Focal secretory changes||24.1%|
(precursor of infiltrating ductal cancer)
In other words, a very high percentage of women have ‘cancerous’ lesions in their breasts. Yet, around 4% of women die of breast cancer. In the words of the authors of this study…
‘….in any case, the high frequency of ductal hyperplasia and CIS (carcinoma in situ) 25.6% suggests that only a small proportion of these must ever progress to invasive carcinoma.’
If only a small proportion of ‘cancerous’ lesion actually progress to invasive carcinoma, then the majority of those found would never cause any harm to the woman. Thus overdiagnosis must be a very major problem indeed. Ironically, the more detailed an accurate screening beomces, the more overdiagnosis will occur.
Anyway, I was unsurprised to see the recent headline:
‘Breast cancer screening does ‘more good than harm’ http://www.bbc.co.uk/news/health-19571173
‘Breast cancer screening saves the lives of two women for every one patient who receives unnecessary treatment, according to a major European review. There has been a fierce debate about the use of screening, and policy is being reviewed in England.
The latest study, published in the Journal of Medical Screening, said at least seven lives were saved for every 1,000 women screened. Health charities say the findings will provide further clarity for women. Tens of thousands of women die from breast cancer across Europe each year. The effectiveness of screening programmes across the continent was evaluated in a series of studies.
It concluded that for every 1,000 women screened, between seven and nine lives were saved and four cases were over-diagnosed.. Mammograms spot dangerous tumours, increasing the chances of survival, but also detect lumps that are essentially harmless, exposing some women to undue anxiety and surgery.
Screening doesn’t just save lives today or tomorrow, it saves lives 10-20 years down the line” Prof Stephen Duffy Queen Mary, University of London.’
I know that there is no possible way that anyone can know that for every seven and nine lives ‘saved’ four cases were overdiagnosed. This is scientific nonsense. The reality is that more cases must have been overdiagnosed than future invasive cancers diagnosed.
I have asked someone to forward me the full studies on which this BBC story was based. I have only one part of it so far, and it is a part that worries me greatly, for it makes the following statement.
‘What these papers tell us is that the time has come to move away from relying solely on the older randomized trials of mammographic screening for the evidence-base, and to use data regularly collected and monitored from service screening programmes, with proper statistical analyses in addition to the results from the randomized trials. The authors of these articles set a precedent for how this could be done effectively.’ http://xa.yimg.com/kq/groups/14947167/193204470/name/benefits%20and%20%20harms%20of%20mammograms%202012.pdf
The time has come to move away from relying on randomized trials!
Once you move away from randomized trials you are no longer doing science. You are doing dogma. At which point the truth can never, ever, be obtained. When someone tells me we should use data regularly collected and monitored from service screening programmes with ‘proper’ statistical analysis – I know that THE TRUTH is being buried.
So long science.