Breast screening: truths, harms and costs

There was some choice reading in the bmj recently: ‘Editor’s Choice – Breast screening controversy continues’ Fiona Godlee, editor, (BMJ 2013;346:f477) in which she flags up calls for more honest information on the harms of screening (BMJ 2010;340:c3106, BMJ 2011;343:d6894); the Marmot committee report summarised by Nigel Hawkes at the time (BMJ 2012;345:e7330);  Michael  Baum’s article (below) (doi:10.1136/bmj.f385) which criticizes the Marmot report because its estimates of harms ‘was based on three old and shortish randomised trials, and the analysis takes no account of the improvements in treatment since these trials were done, which will reduce the benefits of screening. Nor does it make use of more recent observational data. With these data included, estimated rates of overdiagnosis as a result of screening increase to up to 50%.’; and Jolyn Hersch and colleagues’ paper which looks at women’s attitudes to screening and ‘overdiagnosis’ (doi:10.1136/bmj.f158)  – commenting ‘Attitudes might also harden if we were less coy about what we mean by overdiagnosis. In almost all cases of screen detected breast cancer, overdiagnosis means overtreatment.’

 While in another editorial, Cliona Kirwan sees the benefits of breast cancer screening being eroded by more effective and less harmful treatments (doi:10.1136/bmj.f87) and asks, ‘At what stage must we seriously consider whether this screening is a good use of £96m of the NHS budget?’ (www.cancerscreening.nhs.uk/breastscreen/cost.html).

Side effects breast cancer treatment, lung cancer and heart attacks

A blog written by a medical professor nicely summarises Prof M Baum’s piece in the bmj last week (see earlier post re Fiona Godlee):

http://ripe-tomato.org/2013/01/27/harms-from-mammography/

‘…Screening reduces breast cancer mortality.  But for every death prevented three women will have their breast unnecessarily removed or irradiated. The radiation will cause at least as many other deaths from lung cancer and heart attacks as the screening prevented. Maybe more. Still want it?... Baum is professor emeritus of surgery at University College London, was chief investigator of many key breast cancer trials, and knows what he’s talking about.’

Breast screening, lead time bias and getting the message across ‘Five year survival rates can mislead’ say Gerd Gigerenzer and Odette Wegwarth in the bmj this week and go on to explain why an increase in survival from 44% to 82% is not evidence that screening saves lives, beginning with ‘lead time bias’.

(If a cancer is found by screening when there are no symptoms it is described by patients and screening enthusiasts as having been found ‘early’ and patients claim the early finding ‘saved my life’. But no-one can know how long it had been there. And this ‘early’ finding can simply extend the time a person is a diagnosed cancer patient; the time from diagnosis to death is longer than it would have been if the cancer had been found later when symptomatic. So, this does not show screening saves lives, it only appears to. This explanation is not as comforting or welcome as ‘screening saves lives’ so is often ignored.) “This point has been made many times before. But the message has not yet reached every doctor.”

BMJ 2013;346:f548

http://www.bmj.com/content/346/bmj.f548?etoc=

Rich reading from rapid responses

A recent rapid response to Professor Michael Baum’s bmj article ‘Harms from breast cancer screening outweigh benefits if death caused by treatment is included’ (http://www.bmj.com/content/346/bmj.f385)- by Owen P Dempsey GP (Manchester Metropolitan University) – is an interesting and original approach which exposes much of what is wrong with the push for screening to continue and flags up ‘compelling contradictions in the discourse of the UKBCSP’.

Following Professor Sir Mike Richards’ comments that most UK ‘experts’ didn’t ‘trust’ the findings of the Nordic Cochrane review by Gotzsche et al, ‘such comments have remained unsubstantiated by any published evidence according to McPherson who alleges he was quietly told to cease asking for citations to support these claims by the mysterious UK experts. But, and here is the first puzzle, why would the Cochrane review not be ‘trusted’, and why would there be calls for a UK government and breast cancer charity sponsored so-called ‘independent’ review when a Cochrane review had just been published?’

http://www.bmj.com/content/346/bmj.f385?tab=responses