There is some choice reading in the bmj this week for those interested in breast screening issues, beginning with ‘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).
Harms from Breast Cancer Screening outweigh benefits if death caused by treatment is included.
Does screening for cancer improve length or quality of life?
‘All other outcomes are surrogates’, states Professor Michael Baum, his claims substantiated by cited research in Personal View, bmj 23 January 2013. Apparently, the clinical trials of screening for breast cancer which informed the recent Marmot Review on breast screening did not measure quality of life. ‘A surrogate for that might be mastectomy rate in screened compared with unscreened populations. On that measure alone, screening fails: the hazard ratio for mastectomy of 1.2 favours the unscreened population.’
As to length of life, the Marmot Committee relied on cause specific mortality, rather than all cause mortality, which includes deaths caused by cancer treatments. ‘The ProtecT trial of prostate specific antigen screening for prostate cancer gives equal weight to cause specific and all cause mortality by accepting that overdiagnosis and overtreatment might lead to an increase in all cause mortality’ says Professor Baum and goes on to estimate the additional non-breast cancer deaths that might be the consequence of screening for breast cancer.
Regarding ‘overdiagnosis’, he cites, a paper published shortly after the Marmot Report: ‘Effect of three decades of screening mammography on breast-cancer’, which gives an estimate approximately ‘30% of all cancers, or 50% of those detected by screening, are overdiagnosed each year in the United States’ (similar to the Nordic Cochrane Centre conclusions). Which means 70 000 women a year are told that they have breast cancer, yet their ‘cancer’ would never become a problem. The NHS Breast Screening Programme’s extended age range means thousands more women than before would be exposed to risk and suffer harms without any benefit.
Estimates of benefits and harms based on trials reported 20 to 25 years ago, as described in the Marmot report, are dismissed as ‘irrelevant to the modern practice of medicine’.
He raises two more important points: 1) as breast cancer treatments improve, the impact of screening necessarily becomes smaller. 2) as overdiagnosis rates increase then the importance of the relatively rare lethal toxicities of treatment increase.
As a former breast cancer patient and patient advocate, I am concerned that the Marmot Report alone will inform the contents of the new breast screening information. Half truth is no truth. BMJ 2013;346:f385
Women’s views on overdiagnosis in breast cancer screening: a qualitative study
Not surprisingly, women’s understanding of ‘overdiagnosis’ (disease that would not present clinically during the woman’s lifetime) may vary. Learning of this considerable harm comes as a surprise after decades of being told ‘screening saves lives’, because it has not been mentioned in the information given to women invited for breast screening.
A research paper in the bmj by Jolyn Hersch and colleagues in Sydney looks at women’s responses to information about the nature and extent of overdiagnosis in mammography screening (detecting disease that would not present clinically during the woman’s lifetime) and explores how awareness of overdiagnosis might influence attitudes and intentions about screening.
Women’s responses to learning about overdiagnosis varied according to estimates of its magnitude. The information raised concerns for some women, ‘not about whether to screen but whether to treat a screen detected cancer or consider alternative approaches (such as watchful waiting)’ , while information preferences varied – many women considering it important to take overdiagnosis into account and make informed choices about whether to have screening, but many wanted to be encouraged to be screened.
The paper concludes ‘…the effects on (women’s) screening intentions may depend heavily on the rate of overdiagnosis’ and ‘overdiagnosis will be new and counterintuitive for many people and may influence screening and treatment decisions in unintended ways, underscoring the need for careful communication.’