Mammogram risks and benefits: Overdiagnosis and misfear are not saving lives.

How Cancer Screening Makes Healthy People Sick

How Cancer Screening Makes Healthy People Sick

Health and medicine explained.
Feb. 14 2014 8:08 AM

Misfearing Breast Cancer

More evidence that routine mammograms make healthy people sick.

Less than 7 percent of breast cancers are diagnosed in women younger than 40.

Photo by Jupiterimages/Thinkstock

This article originally appeared in The Last Word on Nothing.

What’s the No. 1 killer of women? It’s a question that practitioners asked every new patient at a clinic where physician Lisa Rosenbaum once worked, and she hasn’t forgotten the answer given to her by one middle-aged woman with high blood pressure and elevated blood lipids. “I know the right answer is heart disease,” the patient told Rosenbaum, “But I’m still going to say ‘breast cancer.’ ”

Rosenbaum recounts this experience in a perspective published this week in the New England Journal of Medicine, which follows on the heels of a long-term study published online this week in BMJ that found no benefit from screening mammography. The two papers make fine companions.


The Rosenbaum commentary explores a phenomenon that Cass Sunstein dubbed “misfearing”—our human nature to fear instinctively, rather than factually. Rosenbaum’s patient’s first answer is correct—heart disease kills more women than all cancers combined, yet breast cancer seems to invoke far more fear among most women. “What is it about being at risk for heart disease that is emotionally dissonant for women?” Rosenbaum asks. “Might we view heart disease as the consequence of having done something bad, whereas to get breast cancer is to have something bad happen to you?”

I don’t know the answer to this question, but I suspect that Rosenbaum is onto something. Studies show that women—and doctors—grossly overestimate their risk of developing breast cancer and dying from it. One study published in the Journal of the National Cancer Institute found that women in their 40s overestimated, by a factor of 20, their risk of dying from breast cancer during the next decade. I have to think that the media is partly to blame.

Less than 7 percent of breast cancers are diagnosed in women younger than 40 (the median age at diagnosis is 61), but when the disease strikes younger women, it tends to be more aggressive and less responsive to treatment than it is in older women. Scary stories like those of Susan G. Komen, who died of breast cancer at age 36, invoke fear, and for good reason. Komen did not bring her cancer upon herself. Her disease was random, undeserved, and very aggressive. And if you flip through the women’s magazines during their October “breast cancer awareness” extravaganzas, most of the stories you’ll read are about beautiful young women like Komen who were diagnosed at a young age. The way to prevent such a fate, most of these stories will tell you, is obvious—screen early and often.

This solution is the only reasonable option if you think of breast cancer as a relentlessly progressive disease that will inevitably kill you if you don’t remove it in time. That story about breast cancer—I call it the “relentless progression” model—has truthiness on its side. It makes common sense and offers a measure of comfort: Every cancer can be cured if you just catch it in time.


There’s just one problem, as I’ve written here numerous times before—research has shown that the relentless progression model is wrong. Despite the one-size-fits-all name, breast cancer is not a single disease, and as the science of tumor biology has advanced, researchers have come to understand that not every breast-cancer cell is destined to become one of the life-threatening varieties. It’s only when cancer spreads to other parts of the body—a process called metastasis—that it becomes deadly, and it’s now clear that not every breast cancer is fated to leave the breast. If you detect an indolent cancer early, there’s no life to save.

The BMJ study published this week adds another large mass of evidence to an already rather large pile suggesting that most of what mammography has done is turn healthy people into sick but grateful cancer survivors. The Canadian study followed nearly 90,000 women across several decades and found that those who received screening mammograms were no less likely to die of breast cancer than the women in the study randomly assigned to skip the tests, but they were prone to getting treated for breast cancers that would have never harmed them. (The problem, of course, is that we can’t yet distinguish the bad ones from the harmless ones, so once a cancer is detected, we must assume it’s the worst kind, lest we undertreat it.)

The BMJ study calculated that 22 percent—more than 1 in 5—breast cancers diagnosed by a screening mammogram represented an overdiagnosis. These were breast cancers that did not need treatment, and the women who received these diagnoses needlessly underwent treatments that could damage their hearts, spur endometrial cancer, or cause long-lasting pain and swelling.

The true rate of overdiagnosis is almost certainly higher, because the analysis excluded ductal carcinoma in situ, a precancer that accounts for 1 in every 4 breast cancers detected via screening. Experts are currently debating whether to remove the word carcinoma from this condition, as was done for a precancerous cervical lesion. Studies show that simply mentioning the word cancer leads patients to opt for more aggressive treatment.


It’s time to shift our objectives. The glossy magazine stories, awareness brochures, and mammography proponents like the American College of Radiology have set their sights on the wrong goal. The American College of Radiology’s criticism of the BMJ study focuses on the number of cancers detected, but that’s the wrong objective. We should be aiming to save lives, not create as many cancer patients as we possibly can.

No one wants to get diagnosed with cancer. You only benefit from a cancer diagnosis if that cancer is destined to kill you and the diagnosis allows you to treat it in a way that prevents you from getting sick and dying. And that’s where things get complicated, because treatment for cancer makes most people feel pretty lousy. It disrupts their lives in a major way. Even a relatively early stage breast cancer can cost you your hair, part or even all of your breast or breasts, and months of treatments that make you feel tired and sick. These treatments are totally worth it if it means that you avoid dying from the cancer. But if they’re aimed at curing a cancer that was never going to become deadly, then what early diagnosis has actually done is made a healthy person sick. I think it’s safe to say that no one wants that. Treatments and awareness about breast cancer seem to have created most of the improvements in breast-cancer outcomes, and we should celebrate those accomplishments.

Yet despite all the evidence showing that current mammography guidelines are causing more harm than good, I don’t expect them to change without a fierce battle. After the 2009 fight over the U.S. Preventive Services Task Force guidelines, the lines were drawn and most experts took sides. Once that happens, new evidence is unlikely to shift anyone’s opinion. Instead, it will cause those who oppose cutting back on mammography to dig in their heels and seek uncertainty in the data to confirm their prior belief that mammography saves lives. Once people have made up their minds, it’s difficult to open them up again, and a determined mind is prone to confirmation bias. Even when the numbers point to heart disease as the most dangerous killer, it’s hard for facts to overcome conditioned fear.

Mammography proponents like Harvard’s Daniel Kopans are surely right that mammography has saved some lives. But the more important question is whether they’ve helped more women than they’ve harmed, and the evidence is now clearly pointing to no.

This article originally appeared in The Last Word on Nothing. Tagline: “Science says the first word on everything, and the last word on nothing.” —Victor Hugo.