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Few women aware of overdiagnosis and overtreatment risk after mammography, U of M study finds

REUTERS/Enrique Castro-Mendivil
Only 16.5 percent of the women were aware that routine screening can lead to overdiagnosis, and only 18 percent were aware that it can lead to overtreatment.

We’re nearing the end of yet another Breast Cancer Awareness Month with most American women still remarkably unaware about one important breast cancer-related issue.

Less than 1 in 5 women know that the benefits of routine mammograms are often overstated, while the risks — overdiagnosis and overtreatment — are downplayed.

Furthermore, when presented with statements of fact regarding the overdiagnosis and overtreatment of breast cancer, less than 1 in 4 women believe them.

Those numbers come from a University of Minnesota study published earlier this month in the journal Medical Care. A research team led by Rebekah Nagler, an assistant professor of journalism, analyzed data collected from a nationally representative sample of 429 women, aged 35 to 55.

They found that only 16.5 percent of the women were aware that routine screening can lead to overdiagnosis, and only 18 percent were aware that it can lead to overtreatment. The researchers also found that only about 21 percent of the women found these two factual statements believable:

  • Some breast cancers found by mammograms are so slow-growing that they would not have caused any health problems for women in their lifetime.
  • Some breast cancers that are treated (such as with surgery or medications) would not have needed such treatment after all.

The study's findings represent a problem. For it means that most women are not making informed decisions about mammography screening.

“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 reevaluation of aggressive screening strategies,” Nagler and her colleagues write. “For example, a recent Danish study estimated that one third of breast cancers detected by mammography represent overdiagnosis.”

“Ensuring that patients understand harms such as overdiagnosis and overtreatment is central to informed decision making about cancer screening and, in turn, the promotion of patient-centered care,” they add.

To learn more about the study and its implications for women’s health, MinnPost recently spoke with Nagler. An edited version of that discussion follows.

MinnPost: Since its inception 32 years ago, Breast Cancer Awareness Month has often seemed like “Get a Mammogram Month.” As your study makes clear, there’s little awareness among women that routine mammograms can lead to overdiagnosis and overtreatment. Why do you think that message has had such difficulty getting through?

Rebekah Nagler: Part of it is because the message has not been, on balance, as prevalent as the get-screened message. There is this push for prevention and early detection. The exposure to that message has been greater than to the message about the risks and potential harms of screening. It has not had the same level of attention.

MP: There seems to be a resistance to it as well.

RN: I don’t know if we can yet say whether or not there is entrenched resistance to it. I think we’re too soon in that journey to know if there is resistance or just not a ton of awareness.

MP: Let’s start with overdiagnosis. What do women need to know about it in terms of risk?

RN: I should first say that I am a health communication researcher. I’m not a physician and certainly not a radiologist. But the definition of overdiagnosis is typically that some of the cancers — in this case breast cancer — that are found by mammograms are so slow-growing that they would not have caused any health problems for women in their lifetime. These are what doctors would call indolent cancers.

The estimate for how much overdiagnosis we have with breast cancer is as high as 30 percent. It’s important for women to understand this possibility. The major professional organizations  — the American Cancer Society, the U.S. Preventive Services Task Force — have asked women, especially women in their 40s, to play a pretty active role in decision-making about when they want to start [breast cancer] screening. And so I think the key thing is for women to understand this idea of overdiagnosis so that they can make an informed decision. Some women may find it to be a tolerable risk. Other women may not.

MP: The concern about overdiagnosis is, of course, that it then leads to overtreatment. What should women know about the risks of overtreatment?

RN: Overtreatment follows overdiagnosis mainly because the science is not far enough along to be able to predict which of those cancers are actually going to be fast growing versus slow growing. If we could do that I think we wouldn’t have the same overtreatment issue. The problem is that right now doctors can’t predict that. And so, if they find a cancer, they have to treat it. What type of treatment will depend on what the actual diagnosis is, but it could include surgery and, in some cases, medications like hormonal therapies.

MP: Amazingly, three in four women in your study expressed disbelief when presented with information about overdiagnosis and overtreatment, and even more said those issues were ones they didn't need to consider when making their own mammography decisions. Why are so many women reluctant to even consider the evidence?

RN: We’ve heard the drumbeat around screening for a long time. Women have heard a lot of the pro-screening message and less of the concerns about the risks of screening, so part of the resistance could simply be that lack of familiarity. In general, when we’re faced with information that conflicts with our prior [views] we tend to resist it. That’s just a natural human process. I think the jury is out in terms of how women will respond to these issues moving forward, but at least we have some hint here that we may need better communication around these risks.

MP: College-educated women in your study were more aware of the problem of overdiagnosis than women with less education, but they were less aware of the problem of overtreatment. Do you know why that would be?

RN: We don’t know why. This is the first study, to my knowledge, that’s really asked. It could be that it was simply an artifact in this particular sample. We’ve observed it, but we need to see if it replicates [in future studies].

MP: You also found that women with a good, regular source of medical care were less likely to believe the argument for overdiagnosis.

RN: Yes, women who had a usual source of medical care were generally a little more resistant. It could be that they just have had more opportunities to speak with clinicians, and in speaking with clinicians they’ve sort of heard a lot about the benefits of screening and perhaps less about the risks. That could really explain that.

MP: The biggest predictor in your study of whether women find statements about overdiagnosis and overtreatment believable, however, was a prior history of mammograms. That was particularly true of women who had had a mammogram within the previous year. They were less likely to believe that overdiagnosis and overtreatment were problems. Why do you think that is?

RN: We know that past behavior is a one of the strongest predictors of future behavior. I think it would make sense that women who’ve been getting mammograms consistently for years would value them. They have strong screening priors, as psychologists would call them. We latch on to them the way we do with any other sort of strong value system or belief we have — and that can guide our future behaviors and decisions.

MP: Patient/doctor communication also has a lot to do with women’s attitudes toward routine mammography, right? Many doctors over-emphasize the benefits and talk little, if at all, about the risks.

RN: Right. Other studies have shown this — studies that have been done with providers. Clinicians themselves are generally more aware of the benefits of screening — not just breast cancer screening, but screening more generally — compared with the risks. That could translate into a differential communication pattern when they’re talking with patients about these procedures and tests. Again, I think we need to know more, but that’s certainly a possible explanation.

MP: What can be done to help women become more aware of the risk of overdiagnosis and overtreatment with routine breast cancer screening so that they can make more informed decisions?

RN: This is particularly important for women in their 40s. I do think that talking with your [health care] provider is probably a really useful step. [Some efforts are under way] to help providers better communicate about these issues. We’re getting there, but for women to play an active role in decision making — to really do that — they’ll need information [about the harms as well as the benefits] of screening.

FMI: You’ll find an abstract of the U of M study on Medical Care's website, but the full study is behind a paywall. You’ll find an explanation of how routine mammography can lead to overdiagnosis and overtreatment, at the Breast Cancer Action website.

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Comments (2)

Prostate cancer getting same questioning?

Appreciate this article but it makes me wonder if the same research has been done for men and Prostate cancer.


Your guest stated that "the science isn't there to determine which cancer will be fast or slow growing". So its overtreatment for a woman to decide to under go treatment for a disease which "might" be fatal, but maybe not, but for which the answer to that question isn't clear. Sounds more like prudent to me.