Abstract

In February 2014, BMJ published the findings of the twenty‐five‐year follow‐up of the Canadian National Breast Cancer Screening Study. Data from this study indicate, the article reports, that mammography screening in women aged forty to fifty‐nine does not reduce the death rate from breast cancer “beyond that of physical examination alone or usual care in the community.” Based on these findings, the authors suggest it is time to reassess the value of mammography screening. This report has reignited an often acrimonious debate about the value of screening people for various diseases when no symptoms are present. As with the recent controversy about the value of prostate cancer screening, the debate about mammography screening offers two important lessons about science, technology, and medicine: scientific evidence carries serious limitations, and we need a better approach to assessing it than the current fragmented one.