In a New England Journal of Medicine “Perspective” article, Nikola Biller-Andorno, MD, PhD, of the University of Zurich and Harvard Medical School, and Peter Jüni, MD, of the University of Bern, provide the rationale for a recent report by the Swiss Medical Board advocating the phasing out of mammography screening programs in Switzerland.1 The board recommended that no new systematic mammography screening programs be introduced and that existing programs be subject to a time limit.2 The report also emphasized that the quality of all forms of mammography screening should be evaluated and that women should receive clear and balanced information on the benefits and harms of screening.
Drs. Biller-Andorno and Jüni were members of the nongovernmental board, the recommendations of which are not legally binding. The authors, a medical ethicist and a clinical epidemiologist, were joined on the board’s expert panel by a clinical pharmacologist, an oncologic surgeon, a nurse scientist, a lawyer, and a health economist.
Benefit and Harm
As related by the authors, based on review of available evidence, it is estimated that systematic mammography screening might prevent approximately 1 death from breast cancer for every 1,000 women screened. There is currently no evidence that this benefit has an effect on overall mortality.
Weighed against this benefit is the likelihood of harm. For every breast cancer death prevented in U.S. women over 10 years of annual screening beginning at age 50 years, it is estimated that 490 to 670 women would have a false-positive mammogram with repeat examination, 70 to 100 would undergo unnecessary biopsy, and 3 to 14 would have an overdiagnosed breast cancer that would never have become clinically apparent.3
Old Data
The authors note that three major concerns arose during expert panel review of evidence on the effects of screening. First, evidence of benefits appears to be largely based on a series of re-analyses of predominantly outdated trials, the first of which began 50 years ago and the last of which began in 1991.4
Given that none of the trials include data reflecting the dramatic improvement in prognosis of breast cancer that has occurred in the more modern era of breast cancer treatment, the authors ask, “Could the modest benefit of mammography screening in terms of breast-cancer mortality that was shown in trials initiated between 1963 and 1991 still be detected in a trial conducted today?”
Burden of Harms
Second, the authors note being struck by “how nonobvious it was that the benefits of mammography screening outweighed the harms.” They observe that the widely cited relative risk reduction of approximately 20% in breast cancer mortality associated with mammography5 comes at the price of a considerable burden of repeat mammography, subsequent biopsies, and overdiagnosis.
In this regard, they refer to the finding in the recently reported 25-year follow-up of the Canadian National Breast Screening Study that 106 (21.9%) of 484 screen-detected cancers were overdiagnoses. Thus, 106 of the 44,925 healthy women in the screening group in the study were diagnosed with and treated for breast cancer unnecessarily, including unnecessary surgical intervention, radiotherapy, and chemotherapy.6
Further, a Cochrane review of 10 trials involving > 600,000 women indicated no evidence of an effect of screening on overall mortality. This analysis suggested that at best, the small reduction in breast cancer mortality is attenuated by death from other causes and, at worst, the reduction is erased by death due to coexisting conditions or by the harms of screening and associated overtreatment.4
Given these considerations, the authors pose the question, “Did the available evidence, taken together, indicate that mammography screening indeed benefits women?”
Inaccurate Beliefs About Benefit
Third, the authors note that they were “disconcerted by the pronounced discrepancy between women’s perceptions of the benefits of mammography screening and the benefits to be expected in reality.” A survey of U.S. women showed that 71.5% believed that mammography reduced risk of breast cancer death by at least half, and 72.1% believed that 80 deaths would be prevented for every 1,000 women invited for screening.7 In light of data indicating that the relative risk reduction is 20% and that 1 death would be prevented for every 1,000 women screened, the authors ask, “How can women make an informed decision if they overestimate the benefit of mammography so grossly?”
The authors state that the report “caused an uproar” and was rejected by a number of Swiss cancer experts and organizations, with some calling the conclusions unethical. They note, “One of the main arguments used against [the report] was that it contradicted the global consensus of leading experts in the field—a criticism that made us appreciate our unprejudiced perspective resulting from our lack of exposure to past consensus-building efforts by specialists in breast cancer screening. Another argument was that the report unsettled women, but we wonder how to avoid unsettling women, given the available evidence.”
The authors concluded:
It is easy to promote mammography screening if the majority of women believe that it prevents or reduces the risk of getting breast cancer and saves many lives through early detection of aggressive tumors. We would be in favor of mammography screening if these beliefs were valid. Unfortunately, they are not, and we believe that women need to be told so. From an ethical perspective, a public health program that does not clearly produce more benefits than harms is hard to justify. Providing clear, unbiased information, promoting appropriate care, and preventing overdiagnosis and overtreatment would be a better choice.
Dr. Biller-Andorno is from the Institute of Biomedical Ethics, University of Zurich, and the Division of Medical Ethics, Department of Global Health and Social Medicine, Harvard Medical School. Dr Jüni is from the Institute of Social and Preventive Medicine and Clinical Trials Unit Bern, Department of Clinical Research, University of Bern. Dr. Biller-Andorno currently is a member of the expert panel of the Swiss Medical Board, and Dr. Jüni was a member of the panel until August 30, 2013. ■
Disclosure: For full disclosures of the Perspective authors, visit www.nejm.org.
References
2. Swiss Medical Board: [The Board of Experts Swiss Medical Board has approved a report on the “Systematic screening by mammography.”] Press release, February 2, 2014. Available at www.medical-board.ch.
3. Welch HG, Passow HJ: Quantifying the benefits and harms of screening mammography. JAMA Intern Med 174:448-454, 2014.
4. Gøtzsche PC, Jørgensen KJ: Screening for breast cancer with mammography. Cochrane Database Syst Rev 6:CD001877, 2013.
5. Independent UK Panel on Breast Cancer Screening: The benefits and harms of breast cancer screening: An independent review. Lancet 380:1778-1786, 2012.
6. Miller AB, Wall C, Baines CJ, et al: Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: Randomised screening trial. BMJ 348:g366, 2014.
7. Domenighetti G, D’Avanzo B, Egger M, et al: Women’s perception of the benefits of mammography screening: Population-based survey in four countries. Int J Epidemiol 32:816-821, 2003.
