Mammograms: Too Much of a Good Thing?

There are lots of good reasons to try and follow a healthier diet–you lose weight, you feel good, but the main reason–to live a longer, happy, productive life.  Sounds good, right?   And though it may sound deceptively easy, the devil is in the details.  Welcome to the Nutrition Facts podcast. I’m your host, Dr. Michael Greger. 

Today on Nutrition Facts we continue our series on the efficacy of mammograms. As it turns out, for every life saved by mammography, as many as 2 to 10 women are overdiagnosed, and turned into breast cancer patients unnecessarily, along with all the attendant harms of chemo, radiation, or surgery without the benefits

What was the impact of the 2009 shift in recommendations to delay routine screening until age 50? Ironically, mammography rates of women in their 40s may have actually gone up. The thought is that all the media attention may have just reminded women about it, underscoring the need to better translate “evidence…into practice.”

The new recommendations bring the U.S. closer to European standards: mammograms every few years, starting at age 50. In 2015, the American Cancer Society split the difference, and recommended starting at 45 annually, then switching to every other year at 55—suggesting this would decrease the lifetime risk of dying from breast cancer from 2.7% down to under 2%, based in part on a systematic review performed by the Cochrane collaboration, a highly-respected bastion of evidence-based medicine.

The authors of the Cochrane review, however, wrote in to say they used the wrong number, and that if you look at the studies they considered were “adequately randomized,” there did not appear to be any significant “mortality benefit” from mammograms at all, and that the “data certainly do not support the popular idea that [breast cancer] screening saves lives”—accusing the American Cancer Society of being more of “a political organization with financial ties to…the multi-billion dollar [mammogram] industry.”

The Cochrane review they’re talking about concluded that “[t]he studies which provided the most reliable information [evidently] showed that screening did not reduce breast cancer mortality.” If that’s true, then that changes everything. They conclude that “the time has [therefore] come to re-assess whether [routine mammograms] should be recommended for [women of] any age”—which is what the Swiss Medical Board did. They “were struck by how nonobvious it was that the benefits of mammography screening outweighed the harms.” It’s “easy to promote mammography screening [when] the majority of women believe that it prevents or reduces the risk of getting breast cancer and saves many lives through early detection of aggressive tumors.” I mean, if those beliefs were valid, they’d be all for it. “Unfortunately,” they concluded, “they are not, and [so] believe that women need to be told so. From an ethical perspective, a public health program that does not clearly produce more benefits than harms is hard to justify.” Their report, not surprisingly, “caused an uproar.” Critics argued that “the report unsettled women, but we wonder how to avoid unsettling women, given the available evidence.”

If you ask women what they perceive to be the benefits of regular mammogram screening, they think it cuts the risk of dying from breast cancer in half. First of all, the risk of dying from breast cancer regardless is smaller than most women think, and the reduction in risk—the differences in size—is much smaller, maybe only one in a thousand women benefits. But hey, doesn’t saving the life of even one in a thousand women make it all worth it? Imagine if you were in that one-in-a-thousand families whose mom was saved. But, that may not be true.

One in a thousand women screened may not die from breast cancer, but there’s “no evidence to suggest that overall mortality was affected,” which would mean no lives are actually saved. There’s been 10 randomized trials of mammogram screening, and not one has ever showed “an overall mortality benefit.” Wait. How does that make sense? If mammograms prevent one in a thousand women from dying from breast cancer, then the only way no lives are saved is if mammograms ended up somehow leading to the deaths of one in a thousand healthy women, and that’s preposterous, right?

Let me introduce the concept of “overdiagnosis”—the fact that some of the tiny tumors picked up on mammograms may have never progressed, or even disappeared on their own. And so, had they not been picked up, the women would have been none the wiser: would have never been affected by it, or even known they had it. But once you pick up a cancer on a mammogram, you have to treat it, since you don’t know what it’s going to do. But, in some cases, the overdiagnosed cases where it would never hurt you, you’re treating the breast cancer unnecessarily.

How common is that, though? “For every life saved by mammography, [as many as] two to 10 women are overdiagnosed”—meaning turned into breast cancer patients unnecessarily, along with all the attendant harms of chemo, radiation, or surgery without the benefits. Harms can include death. Imagine being in the family whose mom was killed.

The concern is that unnecessary radiation treatments “may kill…as many as” are saved; hence, the no evidence of net mortality benefit. Radiation treatments to the chest increase the risk of dying from heart disease and lung cancer. Now, those may be acceptable risks, if you actually have breast cancer that would otherwise kill you. Treatments that are beneficial for real patients can be lethal for those who never should have been treated in the first place.

Even if mammograms don’t save your life, might they save your breast? I mean, if you catch a tumor early, maybe you can avoid a mastectomy? The opposite may actually be true. The Cochrane researchers explain that that’s why they published their report. They thought it was important for women to know that “screening [may increase] their risk of losing a breast.”

Basically, mammograms have “been promoted to the public with three simple promises that all appear to be wrong:…Screening does not seem to make the women live longer; it [instead may unnecessarily] increase…mastectomies; and cancers are not caught early…” It may take decades for a tumor to grow large enough to be picked up on a mammogram and, even when they are, they may not grow any further.   That’s the concern, we’re catching too many. “There is so much overdiagnosis that” if a woman really doesn’t want to become “a breast cancer patient,” maybe they should “avoid [mammogram] screening” altogether. But, if you have breast cancer, don’t you want to know?

“The small probability that a woman may avoid a breast cancer death must be weighed against the more likely scenario that she may have a false-positive…[or] false-negative result…, or most critically, [a] diagnosis and treatment of cancer that would otherwise not have threatened her health or even come to her attention.”

Odds are most women will get at least one false-positive mammogram in their lives, but thankfully most women who are called back for further testing of a suspicious mammogram finding do not end up having cancer after all.  Here are the consequences of false-positive mammogram results.

 In response to the Swiss Medical Board’s recommendations against women of any age getting routine mammograms, critics suggested that instead of phasing out screening programs completely, we should leave it up to each woman individually to make her own judgment, once she’s “fully informed” about the pros and cons. “On the basis of the same information, some women will choose screening, and others will not.” I agree—that’s why I’m doing this video series to lay out the benefits and the harms.

When it comes to medical treatments, I think most patients understand there are risks and benefits: drugs can have side effects; surgeries can have complications. So, you can make your decision based on whether you think the benefits outweigh the risks. But, “patients have been taught to think differently about screening.” What’s the harm? Who wouldn’t want to know if you have cancer? It’s a no-brainer. But, “[i]n reality, the truth is more nuanced. There are benefit and harms to consider in screening—just as there are in treatment.”

In the case of mammograms, “the most frequent harm is a false-positive result,” where they think they see something on the scan, but after further testing—more X-rays, ultrasound, or a biopsy—it turns out to be nothing. Phew. As you can imagine, this can cause a “roller coaster of emotions.” “Experiencing a false-positive result can [be an] agonizing experience…,” sometimes “profoundly” affecting a woman’s life. Some women can get depressed, anxious, lose sleep over it, even months later. Even after getting the all clear, breast cancer worries can persist, even a year or more later. And, beyond psychological effects, if you have to go in for a biopsy, they obviously use local anesthesia during the procedure, but the pain afterwards can sometimes persist for days or weeks.

“These adverse consequences would be less concerning if false-positive mammograms were…uncommon event[s].” Unfortunately, most women will get “at least one false-positive mammogram within 10 years” of annual screening, though the chances that a single mammogram will produce a false positive is only about 10 to 14%.

But, that’s way more than over in Europe, for example, where it’s only like one in 20, or one in 50. That’s thought to be because American radiologists are so afraid of being sued for malpractice that the bar they use is much lower. And, that’s fine for a lot of women. Even if 10,000 women have to go through false positives, many feel it would be worth it to save a life—even many women who have themselves experienced a false-positive result firsthand, so they know what it’s like. Most women don’t even “want to take false positives into account when deciding about screening,” but some women do.

For some, going through a false alarm is no big deal, but for others, it can be really scary. Some women interviewed going through the process were described as being in a state of “[e]motional chaos” facing a possible cancer diagnosis. “Waiting for [the] results” was particularly hard for some women; it was constantly on their minds. But after it was over, many women were able to just brush it off, whereas others had persistent anxiety, even though they were given the all clear.

Studies have noted increased anxiety, on average, even months later, after being called back for a suspicious mammogram that turned out to be nothing. Or, even years later. A study of hundreds of women who experienced a false positive, and some appeared to be suffering the consequences— even years later. They were followed out for three years, and the experience still seemed to haunt them. So, maybe we shouldn’t just dismiss these false alarms.

Regardless, “women should be informed of the [possibility], and reassured that most women who are recalled” back for further testing of a suspicious mammogram finding “do not end up having cancer” after all, so as to put their mind at ease a bit as they go through the process, and wait for the final results. 

And now for a bit of an understatement. As any woman who’s had a mammogram will tell you, excessive breast compression can be painful.  And, coincidentally, it turns out the compression may reduce image quality and cause unnecessary pain.  Here’s the story. 

False-positive results have been described as “the most frequent harm” associated with mammogram screening, but actually it may be pain. “There is a wide variation both in the reported frequency of pain and in…degree of pain felt by women” during mammograms. But, there may be little doubt that “the majority of women feel some degree of pain during” the procedure. Why? Isn’t it just some type of X-ray?

For those unfamiliar, the breast is sandwiched between two plates, and kind of pancaked down. Instructions are typically like, “Slowly apply compression until the breast feel[s] taut,” with a force not exceeding 20 kilograms. That’s 44 pounds! That’s like the weight of a cinder block—no wonder some women experience pain!

Studies have attempted to quantify it are all over the place, with the incidence of pain ranging anywhere from 1% to 93%, depending on how they defined it. The discomfort is enough to keep a proportion of women from not coming back. The typical line you hear is that “Although the compression can [be] uncomfortable and even painful for some women, it only lasts…a few seconds”—a sentiment to which one woman replied, “You tell [the] doctor to come on over [here]…he’s got stuff that can be mashed too, you know…”

“Mammogram compression can cause…bruising, and has led to the rupture of breast implants, cyst[s], and…[blood vessels].” “Women with…dense breasts, are often advised to take [painkillers] or tranquilizers to endure the procedure more comfortably.” Yet, you know, pain is there for a reason. It’s trying to warn us about potential “tissue damage.” There’s at least a theoretical concern that tissue inflammation could wake up dormant tumors, but that’s sheer speculation at this point. Still, I mean, we could try to make them less painful.

The reason they do it is to “reduce breast thickness”—purportedly “decreas[ing] the radiation dose and improv[ing]…image quality.” But when it was put to the test and actually measured, one study found “the radiation dose increased [at higher] compression force[s].” Another study found that about a quarter of women “did not experience a difference in the thickness of their breasts when compression was [eased back a bit],” implying that “more compression was applied than…necessary. …[O]nce minimum thickness is achieved [then] further compression only results in more pain with no benefit to image quality.”

The bottom line is that “pain in mammography is an issue to be taken seriously.” “Recognizing this in the tone and content of patient information and advising on ways to deal with it would show greater respect for patients than [just] blanket reassurance[s].” The reason women aren’t more up in arms may be that “the majority of women feel compelled (by fear or duty) to comply…”, but this just helps the medical establishment push the pain issue “to the margins.”

To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There, you’ll find all the detailed information you need, plus links to all of the sources we cite for each of these topics.

Be sure to check out my new How Not to Die Cookbook.  It’s beautifully designed, with more than 120 recipes for delicious, plant-based meals, snacks, and beverages. All the proceeds from the sales of all my books all go to charity. I just want you to be healthier. 

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Thanks for listening to Nutrition Facts.  I’m Dr. Michael Greger.

This is just an approximation of the audio content, contributed by Allyson Burnett.