How to Balance the Risks and Benefits of Mammograms

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Mammogram

Fact boxes can quantify benefits and harms in a clear and accessible format. 

When it comes to cancer screening, doctors “have too often ignored” the fact that women may place different weights on various pros and cons, so they have just “focused on persuading rather than educating” and letting people make up their own mind. To do that though, “they need some quantification of its benefits and harms” in a clear and accessible format. Enter, “fact boxes.”

Let’s consider an example: In 2014, German physicians recommended transvaginal ultrasounds, in which a probe is inserted to look around, to millions of women to screen for ovarian cancer. Is that effective? What does the science say? Based on a study of hundreds of thousands of women, if you randomize a thousand women to get vaginal ultrasounds and a thousand women to skip the screening, and then follow them out for a decade or so, three of the women who did not get screened will die from ovarian cancer, as will the same number of women who did get screened. So, there was no benefit at all. Instead, 32 of the women who had gotten screened went into surgery, some to have their ovaries removed, because something looked suspicious on the ultrasound, but it turned out to be totally unnecessary. And, one of those women suffered surgical complications—all for naught. Just harms, no benefits, yet millions of women were subjected to the probing, “probably resulting in more than 10 000 women having healthy ovaries removed in just one year.” A boon for the hospitals and the surgeons (and their local BMW dealers), but just pain and suffering for the women.

What would a fact box for mammograms look like? I show one at 1:44 in my video The Pros and Cons of Mammograms. As you can see, each grey circle in the graphic represents one woman. A thousand women were either randomized to skip mammograms or randomized to get screened. After a decade, about five out of the thousand women in the no-screening group will die from breast cancer. So, even without mammography screening, the chances of dying from breast cancer in one’s fifties is less than 1 percent. But, by getting regular mammograms, instead of five out of a thousand women dying from breast cancer, only four in a thousand will die from breast cancer, though the number of women dying overall appears to be the same with or without screening. So, no lives are necessarily saved overall. But, maybe the studies just haven’t had the statistical power to pick up on an overall survival benefit. 

In terms of harms, however, a hundred of the women getting mammograms will be called back for false alarms and maybe even get biopsied, and five will have unnecessary lumpectomies or mastectomies. “A third potential harm, getting radiation-induced breast cancer from the mammography, is not included because only rough indirect estimates (1–5 in 10,000) exist.” 

I show a graphical representation of another study at 2:51 in my video. Researchers looked at 20 years of data from women following the current U.S. Preventive Services Task Force recommendations to get screened every other year starting at age 50. One would expect 200 false alarms over those two decades, but only about 30 would end up getting biopsied. A few cancers would be missed, but, in 15 cases, too many would be found, meaning women would be diagnosed with—and treated for—breast cancer unnecessarily. On the other hand, two breast cancer deaths would be averted, thanks to mammograms, though no overall lives would apparently be saved. 

Not everyone agrees with these numbers, though. At 3:28 in my video, I show the most optimistic numbers I could find per 1,000 women screened. As you can see, there may be up to ten times the benefit for a woman getting mammograms every year for 25 years starting at age 40. This is at the cost of an average of three false alarms for each woman, a one in three chance of getting a biopsy, and about a 1 percent chance of being diagnosed and treated for breast cancer unnecessarily. 

Now, this assumes we’re talking about asymptomatic women at average risk. Women at higher risk, such as those who have already had breast cancer or have BRCA gene mutations, would be expected to benefit much more. For the average woman, though, “there is simply no ‘right’ answer to whether a woman should undergo mammographic screening.” It should be left up to each woman to make up her own mind. 

“We hope that [presenting these] data are sufficient for some women to make the decision about whether or not to be screened. Some may choose to pursue screening, valuing any potential for benefit as warranting the accompanying harms. Others may choose not to,” feeling the potential “harms as being too great to justify pursuing the relatively small benefit.” 

Regardless, how about trying not to get breast cancer in the first place? “Individuals would rather be told to get a quick test every few years than be told to eat well and exercise to prevent cancer [before it starts]. ‘Screening has become an easy way for both doctor and patient to think they are doing something good for their health, but their risk of cancer hasn’t changed at all.’” Indeed, getting screened for cancer doesn’t change their risk of getting cancer in the first place—and this doesn’t apply only to cancer. The same diet and lifestyle that can protect against cancer can also protect against the leading killer of women. As you can see at 4:56 in my video, for example, the annual number of women who died from breast cancer from 2006 to 2010 was under 50,000, while the annual number of women who died from heart disease during that period was over 400,000. And while mammograms may not save lives, we know that lifestyle modifications to prevent heart disease can. So maybe some of those billions of dollars spent every year on mammogram programs could be better spent saving the lives of women.

KEY TAKEAWAYS

  • Without mammography screening, the chances of dying from breast cancer when in your fifties is less than 1 percent. With regular mammograms, instead of about five out of a thousand women dying from breast cancer, four women will.
  • There are myriad harms associated with mammograms, though, including false alarms and overdiagnosis, which can result in biopsies, unnecessary lumpectomies or mastectomies, radiation treatment, and chemotherapy, not to mention radiation-induced breast cancer from mammography and the stress and emotional toll of it all.
  • Even looking at the most optimistic numbers per thousand women screened, which shows there may be up to ten times the benefit for a woman getting annual mammograms for 25 years starting at age 40, that is at the cost of an average of three false alarms for each woman, a one in three chance of getting a biopsy, and about a 1 percent chance of being diagnosed and treated for breast cancer unnecessarily.
  • The hope is for women to be presented with all the data to be able to make informed decisions about whether or not to be screened.
  • Screening has become a replacement for trying to prevent cancer through lifestyle efforts, such as eating well and exercising, because it can be thought of as actively doing something positive for their health despite not changing risk of cancer at all.
  • The same diet and lifestyle—one based on whole plant foods—that can be protective against cancer may also protect against heart disease, the leading killer of women.

There is just so much confusion when it comes to mammography, combined with the corrupting commercial interests of a billion-dollar industry. As with any important health decision, everyone should be fully informed of the risks and benefits, and make up their own mind about their own bodies. This is the final installment in my 14-part series on mammograms, which includes: 

For more on breast cancer, see my videos Oxidized Cholesterol 27HC May Explain Three Breast Cancer Mysteries, Eggs and Breast Cancer and Flashback Friday: Can Flax Seeds Help Prevent Breast Cancer?

I’ve produced so many videos on diet and lifestyle approaches to preventing and treating breast cancer. Just search for them on the site, and all will be revealed.

I was able to cover colon cancer screening in just one video. If you missed it, see Should We All Get Colonoscopies Starting at Age 50?

Also on the topic of medical screenings, check out Flashback Friday: Worth Getting an Annual Health Check-Up and Physical Exam?, Is It Worth Getting Annual Health Check-Ups? and Is It Worth Getting an Annual Physical Exam?. 

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

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