Abolishing Mammography Screening Programs? A View From the Swiss Medical Board

Abstract

This article discusses the results and implications of the recently published findings of the Swiss Medical Board Panel on the benefits and harms of mammography screening programs. The Board was established by regional ministers of public health. Two of its members, a medical ethicist and a clinical epidemiologist, prepared this report. Other members were a clinical pharmacologist, an oncologic surgeon, a nurse scientist, a lawyer, and a health economist. The Board’s members were unbiased in that they were not part of consensus-building efforts by proponents of breast cancer screening. When they undertook this task, the panel was well aware of the controversy in the last 10 to 15 years on this issue. As they examined the available evidence on the overall benefits of screening, both data supporting the value of screening mammography and data that did not, the panel had a number of concerns. Their first concern was whether the modest benefits of screening found in several trials published between 1963 and 1991 would be found in a trial conducted today. And if there are benefits, do the harms of screening outweigh any benefit? The authors discussed the findings of the Canadian National Breast Cancer Screening Study, which earlier this year published its 25-year follow-up study of patients who had regular screening mammography. The data showed that repeat mammography with subsequent biopsies led to overdiagnosis of breast cancers that would never have become clinically apparent. Cancers were detected in 484 of the 44,925 healthy women who were regularly screened. Twenty-two percent of screen-detected cancers were overdiagnosed and received needless surgery, radiation, chemotherapy, and various combinations of these interventions. Another study, a Cochrane review of 10 trials involving more than 600,000 women, found no evidence for a beneficial effect of mammography screening on overall breast cancer mortality. The Board also noted a marked discrepancy between the perceptions of 50-year-old women in the United States on the benefits of screening and the most likely expected benefits. More than 70% of women in a large sample believed that mammography every 2 years starting at age 50 years reduced the risk of breast cancer deaths by at least half over a 10-year period and that at least 80 deaths would be prevented per 1000 women. However, compared with women who do not undergo screening, the most likely scenario among 50-year-old women in the United States using a relative risk reduction of 20% (accepted by most cancer experts as the expected benefit of regular screening) would be prevention of only 1 breast cancer death per 1000 patients. The Board wondered how women who overestimate the benefits of mammography can make an informed decision. In summary, the Board concluded that mammography screening does not reduce the overall death rate from the disease. The modest reduction in the mortality rate from breast cancer is offset by its harms. Overdiagnosis leads to needless biopsies and harmful treatment of women without life-threatening breast cancers. Therefore, the Board recommended that (1) Switzerland should stop introducing new mammography screening programs and phase out existing ones, and (2) all systematic screening programs should be replaced with screening information and that women make individual choices. Most Swiss and American cancer experts strongly criticized the Swiss Board’s findings and recommendations. However, the authors note that it is difficult to justify from an ethical perspective any public health program that produces more harms than benefits.