Is Breast Cancer Over-Diagnosed?

By Jane Farrell

Routine mammograms can lead to over-diagnosis and over-treatment of breast cancer, but most American women aren’t aware of these risks of breast cancer screening, reports a study in the October issue of Medical Care, published by Wolters Kluwer.

What’s more, most women don’t find statements about breast cancer overdiagnosis and overtreatment to be “believable or persuasive,” according to the new research by Rebekah H. Nagler, PhD, of University of Minnesota, Minneapolis, and colleagues. The findings underscore the challenges of accurately communicating these risks so that women can make informed decisions about mammograms and breast cancer screening.

Overdiagnosis refers to detection of cancers that grow so slowly that they would never have caused any health problems during a woman’s lifetime.

The survey study sought to assess women’s awareness and perceptions of overdiagnosis and overtreatment — two of the main potential harmful effects of breast cancer screening. Overdiagnosis refers to detection of cancers that grow so slowly that they would never have caused any health problems during a woman’s lifetime. Overdiagnosis often leads to overtreatment, which refers to unnecessary treatments (such as surgery or medications) that expose women to side effects with minimal health benefits.

“Although it is difficult to pinpoint just how common cancer overdiagnosis is…there is growing expert consensus that the phenomenon is real and may require a re-evaluation of aggressive screening strategies,” Nagler and coauthors write. The authors argue that it is important for patients to understand potential harms such as overdiagnosis and overtreatment so that they can carefully consider whether and when to begin breast cancer screening.

The study was a survey of a nationally representative sample of 429 US women, aged 35 to 55. Only 16.5 percent were aware of the potential risk of overdiagnosis from breast cancer screening, while 18.0 percent were aware of the concept of overtreatment. Women younger than 40 were least likely to have heard about overdiagnosis.

When presented with statements regarding overdiagnosis and overtreatment, most women had negative perceptions. “Fewer than 1 in 4 agreed with and found statements about overdiagnosis and overtreatment to be believable, and even fewer evaluated them as strong arguments to consider in their own mammography decision making,” the researchers wrote.

Women who had recently had a mammogram were “particularly unconvinced” by these statements. Women with a usual source of medical care were also less likely to believe statements regarding overdiagnosis.

Nagler and colleagues believe their findings have implications for communicating with patients about the potential harms of breast cancer screening. In particular, women with a strong history of following advice to get mammograms might be an important target for interventions to improve informed decision-making.

Given evidence that many women view breast cancer screening favorably, it may be challenging for providers to communicate with patients about its potential harms

Given evidence that many women view breast cancer screening favorably, it may be challenging for providers to communicate with patients about its potential harms. The authors’ conclusion: “Rigorous health communication research is necessary to inform communication interventions that could improve patient understanding of overdiagnosis and overtreatment [and] promote appropriate use of screening.”