As a pink tide of breast cancer fundraising events blankets the country this month, a new analysis published today in the Archives of Internal Medicine questions a key piece of the campaign’s rhetoric—that “breast cancer screening saves lives.” Instead, researchers from Dartmouth University have found that the vast majority of women whose cancer is detected through screening don’t derive a survival benefit from it.
The authors of the analysis, H. Gilbert Welch, MD, MPH, and Brittney A. Frankel, of the Dartmouth Institute for Health Policy and Clinical Practice in Hanover, New Hampshire, note that for most women with breast cancer, screening mammography may make no survival difference because their cancer might have been detected and successfully treated without such screening. They also note that that screening may even lead to “overdiagnosis” and treatment-related harm when it detects abnormalities that do not require intervention.
The researchers found, for example, using data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results database, that for a 50-year-old woman whose breast cancer has been detected through screening mammography, the probability that her life has been saved as a result of the screening is only 13%; for many other women, the probability of being saved by screening is even lower.
news@JAMA: We often hear testimonials from women who have survived breast cancer saying that screening mammography saved their lives. What does your study tell us about the impact of screening on survival?
Dr Welch: More often than not, she was not helped. When you hear these stories, you need to understand that there are other possibilities; she may not have been helped or she may have been overdiagnosed.
news@JAMA: Why might screening mammography make no difference for some women?
Dr Welch: Screening always has a mixture of effects. We’ve only talked about ways it might help [in our public health messages]. We’ve exaggerated the benefits and we’ve downplayed the harms.
news@JAMA: What are the potential harms associated with overdiagnosis?
Dr Welch: You may get treatment that can’t help you and can only hurt you. You get chemotherapy or radiation or both for something that was never going to hurt you.
news@JAMA: Are there harms associated with false positives, as well?
Dr Welch: A lot of women have to have a lot more mammograms or biopsies. A lot of women are made to feel totally vulnerable through this process.
news@JAMA: Is there any way to reduce the harms of screening?
Dr Welch: Ironically, we might be able to continue the good we are doing and reduce the harm if we didn’t look so hard. This perception that every woman whose breast cancer is detected through screening is saved has fueled this cycle of looking harder and harder for abnormalities and exacerbates the problem of overdiagnosis.
news@JAMA: What might be an alternative to this cycle of looking harder and harder for abnormalities?
Dr Welch: Looking only for abnormalities that are big—for example, doing biopsies only on masses that are larger than a centimeter.