Mammographic breast cancer screening: after the dust has settled

Abstract

Breast cancer is still a major public health issue worldwide; according to present estimates, 1 million women will be diagnosed with breast cancer this year. There are no longer any countries in which the incidence is truly low. In the European Union, there are 1 million women alive today with breast cancer and over 100 000 deaths each year. Death can frequently occur at an age when a woman has maximal social responsibility. It is a common cause of cancer and cancer death and can frequently be a dreadful disease. Progress in breast cancer control is slow but steady with recent proof-ofconcept in Tamoxifen intervention giving a cause for hope for the future. Clinical and pathological considerations clearly demonstrate that survival following the diagnosis and treatment of breast cancer at an ‘early’ stage is much better than when the disease is locally advanced or metastatic. Mammography can detect tumours at a clinically undetectable stage; such tumours have a very good prognosis and many can be cured by appropriate treatment. Since the publication of the results of the Greater New York Trial and the Swedish Two-County Trial in the 1970s and 1980s, there has been a general consensus that screening for breast cancer with mammography reduces mortality from the disease. The results of these pioneering trials have for the most part been subsequently confirmed by later trials in Sweden, Canada and the United Kingdom. Although some debated issues endure, most notably issues of costeffectiveness of screening in particular age groups, the evidence that screening reduces deaths from breast cancer has grown and the consensus has remained. Results from trials were adequately promising that routine, population screening was either recommended or introduced as Public Health Policy in a number of populations. Questions about the quality of the trial data were raised by G tzsche and Olsen and vigorously debated. This challenge was renewed when The Lancet published a research letter by Olsen and G tzsche describing their overview of the mammographic screening trials and reaching a startling conclusion. It was asserted that ‘y the reliable evidence does not indicate any survival benefit of mass screening for breast cancer,’ and maintain that screening leads to more aggressive treatment. The publication has not prompted any major rethinking of screening policy in the United Kingdom, Sweden, the Netherlands or the United States, and most of the scientific community remains unconvinced by the arguments. To see why, consider the figure (Fig. 1) showing the published results of the mammographic screening trials. Overwhelmingly, the results indicate a substantial and significant reduction in breast cancer mortality with invitation to screening. The data in these trials have undergone repeated independent scrutiny and recent evidence suggests that in organised service screening programmes, the benefit may be greater than that observed in the trials. The situation was in striking contrast to the views of the media and the general public, where frequently major concerns were raised that screening was doing no good and may even be doing harm. The temperature was further raised when the PDQ Committee in the United States, in a highly publicised meeting, then down-graded their position on the quality of the evidence on mammographic screening. The controversy regarding the efficacy of mammographic screening is clearly one of the most important issues in cancer control at the present time. If recent conclusions questioning the efficacy of mammography ARTICLE IN PRESS