The story does not mention the cost of mammography (or of follow up tests and treatments) to the individual, or, collectively, to society. And these costs are substantial. Based on the results of this study, 2,500 women would have to be screened every other year for a decade in order to prevent one death from breast cancer. As the story points out, during that same time 1,000 of those women would have at least one false alarm and 500 would undergo an unnecessary biopsy, thus adding to the price tag. On balance, this story does a fair job of describing the benefits of screening mammography as seen in this study. It reports the apparent 10 percent reduction in breast cancer deaths, while also pointing out that because relatively few women in the 50-69 age group die of breast cancer, that reduction can also be described as cutting the 10-year risk of death from 4.4 per 1,000 women to 4 per 1,000. The second statistic helps counteract popular assumptions about how many middle-aged women die from breast cancer. However, the framing of a story – and who gets the last word – sometimes overwhelms evidence-based explanations earlier in the story. That almost happened with this story, which gives the final word to an advocate of annual breast cancer screening for all women beginning by age 40, which is just the sort of blanket recommendation this latest study calls into question. The story includes a comment that because mammograms detect lumps that would not have become life-threatening, five to 15 women may be treated for every one whose life is saved by treatment. The story oversimplifies the methods used by researchers, saying they compared “women who were similar in most ways, except that one group received mammograms and the other didn’t,” without explaining that this was not a randomized trial where some women were assigned to screening and others weren’t, but rather an observational study that looked at data on women during a 9-year period when Norway phased in mammography region by region. The story does alert readers to some of the limitations of the study: one, that a longer follow-up period might have shown more benefit to screening and, two, that the researchers had no information on whether any of the women received mammograms outside of the national screening program. It’s a tossup for us to grade and, as we do in most such cases, we’ll give the story the benefit of the doubt.
Mammogram benefits more modest than doctors thought