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Effect of population-based screening on breast cancer mortality
The reduction in mortality specifically from breast cancer, demonstrated in the major meta-analyses in the 1980s resulted in public health breast cancer screening programs being set up in many countries, including France. Recent publications have challenged the usefulness of screening, by insisting in particular on the negative effects of overdiagnosis and the lack of any significant impact on mortality. From analysis of the literature and particularly independent reviews published in 2012, we provide some answers for doctors faced with the legitimate concerns of women. These studies confirm that screening in the right age group reduces specific mortality by at least 20% at a cost of overdiagnosis estimated at between 1 and 15%.
Introduction In 2001, a Cochrane review of mammography screening questioned whether screening reduces breast cancer mortality, and a more comprehensive review in Lancet, also in 2001, reported considerable overdiagnosis and overtreatment. This led to a heated debate and a recent review of the evidence by UK experts intended to be independent.
Objective To explore if general medical and specialty journals differed in accepting the results and methods of three Cochrane reviews on mammography screening.
Methods We identified articles citing the Lancet review from 2001 or updated versions of the Cochrane review (last search 20 April 2012). We explored which results were quoted, whether the methods and results were accepted (explicit agreement or quoted without caveats), differences between general and specialty journals, and change over time.
Results We included 171 articles. The results for overdiagnosis were not quoted in 87% (148/171) of included articles and the results for breast cancer mortality were not quoted in 53% (91/171) of articles. 11% (7/63) of articles in general medical journals accepted the results for overdiagnosis compared with 3% (3/108) in specialty journals (p=0.05). 14% (9/63) of articles in general medical journals accepted the methods of the review compared with 1% (1/108) in specialty journals (p=0.001). Specialty journals were more likely to explicitly reject the estimated effect on breast cancer mortality 26% (28/108), compared with 8% (5/63) in general medical journals, p=0.02.
Conclusions Articles in specialty journals were more likely to explicitly reject results from the Cochrane reviews, and less likely to accept the results and methods, than articles in general medical journals. Several specialty journals are published by interest groups and some authors have vested interests in mammography screening.
Early detection of cancer has long been thought to be the first step towards eradicating the mortality associated with the disease. National screening programmes for breast cancer have been implemented in many countries. However, there is controversy regarding the efficacy and optimal methods of screening, which is regularly discussed in articles, at conferences and is apparent in conflicting guidelines. In this article, Nature Reviews Clinical Oncology asks four experts their opinions on some of the pressing questions associated with breast cancer screening.
