The benefits and harms of breast cancer screening

Abstract

Trustworthy assessment of mammography screening necessitates complete and balanced reporting of benefit and harm. However, the Independent UK Panel on Breast Cancer Screening is framing the data.1Independent UK Panel on Breast Cancer ScreeningThe benefits and harms of breast cancer screening: an independent review.Lancet. 2012; 380: 1778-1786Summary Full Text Full Text PDF PubMed Scopus (976) Google Scholar Reporting of harm is incomplete and bias is in favour of possible benefit. In the Summary and Conclusions, the relative risk reduction of breast cancer mortality is reported as 20%, whereas the possible harm of overdiagnosis is reported as an absolute percentage increase: “just over 1% would have an overdiagnosed cancer in the next 20 years”. To use equivalent modes of presentation, the benefit should read something like “just over 0·4% would be prevented from dying of breast cancer in the next 20 years”. Additionally, in the Conclusions, the panel estimates that in the UK about 1300 breast cancer deaths would be prevented every year. But the corresponding figures for overdiagnosis of breast cancer and recalls for additional diagnostic tests, including 25% of recalled women getting a biopsy, are not reported. On the basis of the information in the review,1Independent UK Panel on Breast Cancer ScreeningThe benefits and harms of breast cancer screening: an independent review.Lancet. 2012; 380: 1778-1786Summary Full Text Full Text PDF PubMed Scopus (976) Google Scholar I calculated that there would be around 4300 women with overdiagnosis of breast cancer every year, and about 100 000 recalls and 25 000 biopsies every year (although it is difficult to estimate the recall and biopsy figures from the information provided in the review). Finally, important data on interval cancers are missing, and the costs of screening, including costs of overdiagnosis and overtreatment, should be provided. I declare that I have no conflicts of interest. The benefits and harms of breast cancer screening: an independent reviewWhether breast cancer screening does more harm than good has been debated extensively. The main questions are how large the benefit of screening is in terms of reduced breast cancer mortality and how substantial the harm is in terms of overdiagnosis, which is defined as cancers detected at screening that would not have otherwise become clinically apparent in the woman's lifetime. An independent Panel was convened to reach conclusions about the benefits and harms of breast screening on the basis of a review of published work and oral and written evidence presented by experts in the subject. Full-Text PDF The benefits and harms of breast cancer screening – Authors' replyThese letters variously suggest that the Independent UK Panel on Breast Cancer Screening either understated or overstated the benefits of breast screening and either underestimated or overestimated the risk of overdiagnosis. It was just such divergent views that led to the convening of the panel. The panel heard from expert witnesses who put most of the points contained in these letters to us. Our responses are set out in our full report1 and we give the relevant page numbers below. Full-Text PDF