It’s Ok to Opt Out of Mammograms

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breastcancer

It’s October, which means that my local hardware store is offering a discount to shoppers who wear pink, Allegiant Airlines is selling pink drinks and police officers across the country are donning pink badges, all the name of “breast cancer awareness.” Also known as “pinkwashing,” these pink ribbon awareness campaigns allow people to feel like they’re doing something, without having to think too deeply about the sober facts about breast cancer. Breast cancer screening has failed to reduce the incidence of metastatic disease, and it’s unnecessarily turned healthy women into cancer patients (more on that below).

If you find a lump or something weird in your breast, absolutely get it checked out. In those instances, a mammogram is a necessary diagnostic tool. But screening mammograms — those done when you have no symptoms — have never been shown to decrease overall mortality and may cause tangible harms. For these reasons, I’ve chosen to opt out of mammography, and I based my decision on statistics and science.

For answers to some common questions about the limits of breast cancer screening, see this post I wrote in 2013. I’ve written about the shortcomings of screening for close to 20 years now, and I’m tired of writing the same stories. But since I first wrote the post below in October of 2015, I’ve watched a lot of friends get called back for more tests after a screening mammogram found something that ended up not to be cancer, and those experiences were surprisingly stressful and life-disrupting.

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Before I begin, a disclaimer: I’m sick of writing about mammography. It feels like groundhog day — I’ve been writing the same damn story, over and over and over again, for nearly 15 years. This is at least the fifth time I’ve written a LWON post about mammograms. (See also: Breast cancer’s false narrative, The real scandal: science denialism at Susan G. Komen for the Cure®, FAQs about breast cancer screening, and Breast cancer’s latest saga: misfearing and misplaced goalposts.)

So why I am I writing about mammograms again? Because even though I just published a story at FiveThirtyEight explaining why science won’t resolve the mammogram debate and a feature at Mother Jones asking how many women have mammograms hurt? (the answer is millions) the harms of mammography continue to be ignored or mischaracterized in the media. Every time this happens, I get letters from people asking me to please clarify this point again. Just this past week, a New York Times editorial penned by two breast radiologists and a breast surgeon declared, “Let’s stop overemphasizing the ‘harms’ related to mammogram callbacks and biopsies,” while an op-ed in the Washington Post titled, “Don’t worry your pretty little head about breast cancer” claimed that, “the idea that anxiety is a major harm doesn’t have much scientific support.” (In fact, at least one study has found long-term consequences from a false alarm.)

What both of these opinion pieces miss and what too many women still don’t know is that while 61 percent of women who have annual mammograms will have a callback for something ultimately declared “not cancer,” this isn’t the most damaging problem. Such false alarms are more devastating than they might seem (I can’t think of another recommended medical test with such a high false positive rate), but most women would probably gladly accept this risk in exchange for a reasonable chance to prevent a cancer death.

Here’s the bigger problem: screening mammography has failed to reduce the incidence of metastatic disease and it’s created an epidemic of a precancer called DCIS. The premise of screening is that it can find cancers destined to metastasize when they’re at an early stage so that they can be treated before they turn deadly. If this were the case, then finding and treating cancers at an early stage should reduce the rate at which cancers present at a later, metastatic stage. Unfortunately, that’s not what’s happened.

This graph published yesterday in the New England Journal of Medicine charts the bad news. (The situation is more nuanced for prostate cancer screening, and yet some medical groups have stopped recommending routine prostate cancer screening.)

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Even if it didn’t reduce deaths, mammography might still be useful if it helped patients avoid the most aggressive treatments. But despite claims to the contrary, randomized trials have shown that participation in screening mammography increases the rates of lumpectomy by 30 percent and mastectomy by 20 percent.

A new paper just published by John Keen and Karsten Jørgensen in the Journal of Women’s Health lays out four principles that women need to understand before making a decision to undergo mammography screening.

Principle 1: Screening May Help, Hurt, or Have no Effect

Women are often urged to get screened because it might save their lives. But that’s only one possible outcome, and it’s the least likely one. Here are the possible outcomes if 10,000 50-year-old women have yearly mammograms for ten years.

MammOutcomes

Principle 2: The Most Reliable Statistic for Evaluating the Benefit of Breast Screening is All-cause Mortality

Mammography is often promoted with claims that it can reduce breast cancer deaths by 15 or even 20 percent. But these numbers represent relative, not absolute risks, and they only consider breast cancer deaths. The average woman’s lifetime risk of dying from breast cancer is low — 2.7 percent without screening. Mammography also leads to the treatment of cancers that never threatened the patient’s life, and these treatments can increase mortality. All-cause mortality is the only measure that takes into account the harms from over treatment as well as the benefits from early detection, but “the benefit of breast screening on all-cause mortality is so small that hundreds of thousands of participants are required to test if the effect is there. The randomized trials, including >600,000 women, did not show an effect on total mortality, which tells us that the absolute benefit of the intervention must be quite small, if it is there,” Keen and Jørgensen write.

Principle 3: Some Plausible Screening Statistics can be Misleading

As I wrote here in 2012, some mammography advocates promote screening by claiming that it improves survival times. “The 5-year survival rate for breast cancer when caught early is 98%. When it’s not? 23%,” read one Komen ad. But survival time is a highly misleading statistic, because it depends entirely on when the cancer is diagnosed, not its ultimate outcome. People “overdiagnosed” with cancers that never would have never hurt them will have a 100 percent survival rate, even though their lives were never threatened. The more harmless cancers that screening finds, the better the survival rates look, even as more people are harmed.

Principle 4: Breast Cancer Biology Limits the Screening Window

In the end, it comes down to cancer biology. Some tumors can send out micrometastases very early, when they’re too small to be detected on even the most high-tech mammograms, and others can grow quite large without ever metastasizing. According to Keen and Jørgensen, what we call “early detection” is actually late in a tumor’s lifetime. They calculate that a tumor that’s 10-mm in diameter contains about one billion cells and has undergone 29 doublings. If you assume a median volume doubling time of 260 days, that means the tumor is more than 20 years old.

The median invasive tumor discovered due to symptoms is about 21 mm, and the median screen-detected invasive tumor is 14 mm. Do the math, and the difference in average size works out to about 7 mm or 1.4 years, but “in reality it is smaller because the many small, overdiagnosed tumors exaggerate the difference,” Keen and Jørgensen write. “The time window when screen detection might extend a woman’s life is narrow, as many tumors that can form metastases will already have done so.”

So what’s the takeaway?

None of the mammography studies we have is perfect, but in absolute numbers, there’s no question that far more women are harmed than helped by mammograms. Yet because the comparison is essentially apples to oranges (unnecessary treatments versus a life saved, for instance), deciding whether the harms are outweighed by the benefits comes down to a values judgement, not a math problem. If you’re a woman trying to decide whether or how often to get screened, go back to the chart under principle number one above, look at the numbers and decide for yourself whether the odds are acceptable to you. It’s your body and your choice.


Images: Header photo by Laura Taylor, via Flickr.

Chart of possible outcomes, from JAMA.

Incidence of metastatic breast cancer from NEJM.

6 thoughts on “It’s Ok to Opt Out of Mammograms

  1. Are there any figures on how many out of 10,000 women would have an “unnecessary biopsy” (I am guessing that means a biopsy that did not reveal cancer?) based on a lump found, for instance, during self-exam? I am curious how much mammography actually increases that vs other kinds of detection/screening.

  2. Hi Amy. The answer to your question is in the far right hand bottom corner of the graphic about what happens to the 10,000 women who get screened. For every 10,00 women who get a mammogram every year from age 50 to 59, 940 of them will have a biopsy that does not reveal a cancer. And just to be clear, we are talking here about SCREENING mammography (mammograms done on women without any symptoms). For diagnostic mammograms (those done when someone finds a lump) the numbers are less.

  3. Thank you thank you thank you Christie! This is such an important topic that you continue to shed light on the science and the cultural problem in a way that the general public can truly understand. I have been trying to wave a red flag for years…as I am one of those healthy women turned unnecessarily into a “cancer” patient. Thank you from the bottom of my heart. I will never stop trying to EDUCATE the public about this — and your articles help tremendously! Donna, DCIS 411 (www.DCIS411.com)

  4. Christie, I am so thankful that you continue to write about this topic. It is so important for women to learn all the facts so that they can make an informed choice. It’s sad that medical professionals believe it is their job to make the choice for us. I truly believe that I am a victim of over diagnosis. I was called a cancer patient; until I refused routine mastectomy for stage 0 breast cancer. A cancer which is unlikely to ever cause problems in my life and for which receiving a mastectomy does nothing at all to decrease cancer death mortality. Women need to know that find it early is a myth and that stage o Breast Cancer is NOT breast cancer.

  5. I was put off by the high false positive rate of mammography. A false positive means more invasive follow-up and probably lots of worry, so not good. But when I read that for every 1 life saved through screening, TWO women will be overtreated, I decided to opt out. Overtreatment means the person received full cancer treatment but did not need it. See all of those cancer survivors at the events? A good chunk of them aren’t survivors at all, they are victims of overtreatment, and the treatment they received increases their risk of future cancers. Imagine having a breast removed or going through chemo or radiation when you didn’t need it. It’s really mindblowing.

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