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Breast screening is beneficial, panel concludes, but women need to know about harms

BMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e7330 (Published 30 October 2012) Cite this as: BMJ 2012;345:e7330

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Re: Breast screening is beneficial, panel concludes, but women need to know about harms

Sir,

The panel set up to look into breast cancer screening has thrown a few crumbs of comfort to the dissidents. Yes, they finally acknowledge that over-diagnosis is a serious problem. But they had little choice in the matter – the evidence forced their conversion. Yes, they do agree that participants in screening require better information and this, we are told, will soon available in a revised booklet, though its contents are yet to surface. But, as for the crucial question of whether screening saves lives, they confine themselves to chanting the mantra that it reduces deaths from breast cancer. [1]

The discrepancy between the panel’s estimate of the reduction due to screening in the number of women dying from breast cancer and that of other experts in the field – most notably Peter Gotzsche [2] – is troubling. The effect of screening on disease-specific mortality remains uncertain.

But, in any case, saving lives from breast cancer is not the same as improving overall survival. This is particularly so when there are serious adverse effects from screening, including over-diagnosis. The undeniable point is that screening is harmful. So how are we to know whether breast cancer screening actually improves survival? The answer, of course, is to look at all-cause mortality. [3] But when we do so, we find that screening has no effect on overall mortality. [2] The advocates of screening argue that the reduction in deaths from breast cancer is hidden amongst all of the other causes of death. Yet the same argument may be made about a possible increase in deaths from the adverse effects of screening which would also be undetectable for the same reason.

There is no evidence that breast cancer screening improves a woman’s chances of survival. The same applies to bowel cancer screening. [4] And yet the general view appears to be that both of these screening programmes are beneficial. This is the consequence of very successful campaigns of propaganda and the belief that large-scale randomised controlled trials and epidemiological studies deliver something of genuine value.

After more than three decades of research involving many hundreds of thousands of women, we are still none the wiser about the overall benefits of breast cancer screening. There can be few better examples of the futility of statistics-based research. [4]

James Penston
james.penston@nhs.net

References

1. Independent UK Panel on Breast Cancer Screening. The benefits and harms of breast cancer screening: an independent review. Lancet 2012, doi:10.1016/S0140-6736(12/61611-0.

2. Gotzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database of Systematic Reviews 2011, doi:10:1002/14651858.CD001977.

3. Penston J. Head to head: Should we use total mortality rather than cancer specific mortality to judge cancer screening programmes? BMJ 2011;343;d6395.

4. Penston J. Stats.con – How we’ve been fooled by statistics-based research in medicine. The London Press, November 2010.

Competing interests: No competing interests

06 November 2012
James Penston
Consultant Physician/Gastroenterologist
Scunthorpe General Hospital
Cliff Gardens, Scunthorpe, North Lincolnshire DN15 7BH