PEPs - Clinical Quality and Evidence

Module 2 - Evidence

Example - Breast screening

Image by The Laird of Oldham on Flickr

It’s logical, isn’t it? There is a nasty cancer – cancer of the breast; if we get it early and cut it out, obviously women with the problem will live longer. This has been the predominant belief for the past 30 years or so. However, what is the evidence and how has the evidence changed? Breast cancer screening, when introduced, was based on the belief ¹ that it goes without discussion that catching a cancer early would improve things. Whilst it was considered early on that there may be a down side, it is only very recently that these have become clear. The latest information gained for several different screening programmes confirms that the screening programme has actually caused many women to have unnecessary surgery. This was published in the Lancet  and was attended by a lot of publicity. There is also an excellent NHS Cancer review looking at this paper ² . See also the links to several of the media reports below.

Bid to end breast screening (Daily Mail) - strong views that the screening programme does harm.

'Benefits outweigh the risks': Breast cancer screening saves over twice as many as it harms, scientists calculate (Daily Mail) - Positive views on the screening programme

Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England (PDF Document) (Journal of Medical Screening) - Positive paper on the screening programme

Breast screening advice updated amid controversy over tests (BBC News)

Breast Screening Review (YouTube Video) (Cancer Research UK) - Gives a good summary of the current position

Teacher's Comment

If you read the original study which implies that screening is safe and then compare it to the more recent one where the risks are better outlined;

  • Are there any lessons for the future in your medical practice?
  • Do you think we have heard the end of this story?
  • What could be done to improve the situation?
  • How would you advise a patient who consults you not sure what to do?
  1. Reduction in mortality from breast cancer after mass screening with mammography - Tabar, L. et al (1985) The Lancet 1(8433) 829-832.
  2. The benefits and harms of breast cancer screening: an independent review - Independent UK Panel on Breast Cancer Screening (2012) The Lancet 380 (9855) 1778-1786
  3. Does breast screening do more harm than good? - NHS Choices