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Key points
- Cancer screening can lead to harm as well as provide benefit, but doctors and screening providers fail to warn about the risk..
- Advanced screening finds many earlier smaller cancers that are "overdiagnosed," and would never cause the patient any harm.
- The diagnosis "You have cancer" leads many to choose more aggressive and risky surgery than their particular case requires.
- Those surgeries cause harm, ranging from minor issues to death itself, and cost the health-care system billions of dollars.
October is Breast Cancer Awareness month. The world will turn pink. Recommendations for mammography will be everywhere. But few if any of those recommendations will include information about the harms that mammography can lead to. Yes, harms.
Decades of screening by ever-more perceptive advanced technologies have taught us that not all cancers kill. In fact, many tiny early cancers that screening can now detect never spread, or cause harm, or any symptoms at all. This is true for common types of breast, prostate, thyroid, skin, and lung cancer. They are confirmed as cancer under a microscope based on the size and shape and arrangement of their cells, but these cancers are “overdiagnosed," meaning that we’d never know we had them had screening not found them.
This overdiagnosis can sometimes lead to profound harm. Deeply frightened by the three awful words from our doctor — “You have cancer” — we understandably often pursue more aggressive and potentially harmful treatment than our clinical condition warrants. We have breasts and prostate glands and thyroid glands removed to rid ourselves of cancers that would never have caused any harm, by procedures that have side effects ranging from the minor to death itself. You'd think that doctors and hospitals and advocacy groups that encourage screening would also let us know about those risks, so we can be fully informed as we weigh the pros and cons of mammography.
Yet consider the new Breast Cancer Screening and Diagnosis information resource just published by the National Comprehensive Cancer Network, a group of 32 of the top cancer centers in the U.S. It offers clear and helpful information about breast cancer, and explains mammography and its benefits. But in its 51 pages, there is not a mention of the potential harm of mammography. The words "overdiagnosis” and "overtreatment" never appear. The problems are not even hinted at—even in the section titled “Risk assessment for screening." Nor are they alluded to in the section labeled “Questions to ask," which begins: “In shared decision making, you and your health care provider (HC) discuss the risk for developing breast cancer and agree to a screening schedule.” If you rely on this guide, the discussion of risk includes nothing about the potential harm mammograms can sometimes lead to; only the benefits.
One explanation for this failure to fully inform might be because the authors of the NCCN guidance either deny that overdiagnosis occurs, or don't think it’s that serious. They certainly know about it: Hundreds of research papers have firmly established that it’s a serious problem. So serious, in fact, that scientific panels in France and Switzerland have even suggested phasing out screening mammography altogether, since its life-saving benefits are real but modest (in the U.S., mammography saves between 1 and 2 women per 1,000 screened over 10 years) while the frequency of overdiagnosis and overtreatment leading to real harm is far greater. A recent study of Danish and Norwegian women also found that the harms of overdiagnosis may outweigh the benefits of mammography. The National Breast Cancer Coalition agrees: “Screening mammography of all women has demonstrated only a modest, if any, benefit in reducing breast cancer mortality and is associated with harms that may outweigh those benefits."
A less-benign interpretation would also note that the NCCN consists of institutions that profit from the screening and cancer care they provide. That could also be a part of why many cancer centers promote cancer screening. In fact, some hospitals provide screening free of charge — free screening that generates patients (customers) for those hospitals.
Imbalanced communication about screening that fails to note its risks is not only a problem with breast cancer. Many hospitals aren't informing men about the risks of prostate cancer screening any better than the NCCN does with mammography. A recent review of 607 U.S. cancer centers that recommend prostate cancer screening found that four in ten failed to mention anything about the potential harms of that screening. And one in four failed to suggest that men discuss the pros and cons of screening with their doctors, as recommended by the U.S. Preventive Services Task Force (USPSTF). Major cancer centers accredited by the National Cancer Institute were twice as likely as non-NCI accredited centers to fail to recommend shared decision-making. And eight in ten of all 607 centers also failed to inform men that the USPSTF recommends that testing stop at age 70.
A simpler explanation for all of this may be that society’s emotional relationship with the Emperor of All Maladies has yet to catch up to the progress we’ve made fighting the disease. A cancer diagnosis is no longer the death sentence many still believe it to be. As many as two-thirds of all cancers can now be treated as chronic diseases or cured altogether. Yet two-thirds of Americans, when asked, "What's the first word that comes to mind when you hear the word cancer?” answer "Death."
So we want every tool possible to give ourselves some sense of control against this dreaded threat. Which is why belief in screening is deeper than faith in many religions. Study after study finds that people choose cancer screening even when they are expressly told it’s more likely to harm them than help them. And study after study finds that doctors do the same thing the NCCN has done: Inform patients about the benefits of screening without fully informing them about its risks.
The problem of overdiagnosis of cancer is real, and its cumulative economic and human health costs are enormous. Research for my book due out next year, tentatively titled Rethinking Our Fear of Cancer: How excessive worry about a dread disease does great harm all by itself (in press, Johns Hopkins University Press) estimates that lumpectomies, mastectomies, or double mastectomies for overdiagnosed breast cancer conservatively cost the U.S. health-care system an estimated $2.5 billion. The overtreatment of prostate cancers that would never have caused any harm costs the health care system another $860 million annually.
Individual women considering a mammogram or men thinking about a PSA test don’t care about overall costs to the health care system. They want to know what’s advisable for them, which is what the NCCN booklet and cancer center screening recommendations are supposed to help with. Sadly, people relying on these communications for complete and balanced information to make choices about their health are not getting it. That failure to accurately and fully inform puts people at risk and contributes to significant harm.
