Why new guidelines recommending screening at 40 can’t end the mammography wars

New breast cancer screening guidelines from the United States Preventive Services Task Force give the impression that the decades-long debate over when women should start getting mammograms is settled. The agency now recommends beginning at age 40, reversing the age-50 guideline that had been in place since 2009. This change aligns it with other expert organizations such as the American College of Radiology (though the two still differ on whether women should get mammograms annually or every two years).

Despite this apparent new consensus, the “mammography wars” are not over.

Mammography may be performed 40 million times each year in the United States, but it remains one of the most deeply contested topics in medicine. The recent convergence on age guidelines aside, experts remain divided over how best to define and measure the benefits and harms of mammography, and even over the validity of the very idea of early detection.

This is not because we don’t have enough data. No medical screening — indeed, perhaps no other medical condition at all — has been more scrutinized than the mammogram.

Rather, as my research suggests, the two sides interpret the existing data through different frameworks of meaning. Based on dozens of interviews with scientists, doctors, and patients, I identify two dominant patterns of thought at the heart of disputes over mammography: interventionism and skepticism.

In short, interventionists firmly believe in the benefits of early detection and minimize any possible harms of screening. They are accordingly critical of any effort to delay the age recommendation for mammograms or reduce the frequency of screening.

Skeptics are less confident in mammography screening’s effectiveness and give more weight to the harms of screening, which they also define more broadly than interventionists. They therefore generally advocate delaying the initiation and slowing the frequency of mammography to limit these risks.

Fundamentally, skeptics’ and interventionists’ differing perspectives hinge on whether they believe that early detection is of unambiguous benefit. Early detection has become a default cultural logic, in large part because of long-standing, prominent public health messages that have emphasized the benefits of early diagnosis for many diseases.

Skeptical doctors and cancer researchers question this dominant narrative about the benefits of early detection. As one oncologist put it, “for decades, the message has been, ‘The most important tool is mammography,’ ‘Mammography saves lives,’ and so it’s been … distilled down to sound bites … that leave no room for uncertainty about the benefits and don’t even mention the harms.” Skeptics highlight a range of potential harms one can experience from screening. Some experts even refer to screening as initiating a “cascade of harms.”

The most common harm of mammography is the stress and anxiety associated with repeated screenings due to ambiguous or false-positive results. “We’re trying to find as many cancers as possible,” as one primary care doctor and medical researcher said, “and that’s a recipe for a lot of false alarms.” They also told me, “I mean, we have made a breast cancer scare almost a rite of passage for middle-aged American women.”

Estimates of the rate of false-positive mammograms vary, but one 2020 article in Ethnicity & Health reported a 20% to 65% lifetime risk of receiving a false-positive result, and a 2004 article in the Journal of the American Medical Association found that 35% of participants had had at least one false-positive mammogram. Among the patients I interviewed, nearly three-quarters had been recalled at least once for additional screening or testing. For some, rescreening occurs every time they have a mammogram, a process that can take months to resolve.

Despite this, interventionists tend to dismiss the idea that screening can be harmful. As one director of a cancer center described, “If you had a seesaw and on one side was a 100-pound block of concrete, that’s the benefit. I feel that the harms are equivalent to a feather and that’s what I’m piling on the other side.” A radiologist similarly told me that critics have “exaggerated the negative aspects of screening.” He characterized the harms of screening as minimal — the “anxiety and inconvenience of being recalled” — and “certainly not equivalent to dying from breast cancer.”

One less well-known harm of screening that particularly concerns mammography skeptics is overdiagnosis, which refers to cancers revealed by screening that are slow growing or otherwise not imminently dangerous. Yet when such cancers are found, they are almost always treated, which skeptics argue is more harmful than beneficial, given their relatively benign biological characteristics.

Measuring overdiagnosis is challenging because overdiagnosed cancers are usually treated, and thus are very rarely identifiable as examples of overdiagnosis at the level of the individual patient. Nonetheless, many experts agree that overdiagnosis is real and demonstrable at the population level. “There is a consensus at least in the scientific community that this is a problem, and it’s something that we need to deal with,” said one medical researcher.

From the skeptical perspective, overdiagnosis represents a paradigm shift currently underway in thinking about cancer. As one surgeon and specialist in breast cancer described it, “There is this mantra that one of the best ways of improving the cure for cancer is catch it early.” Early detection is based on a “conceptual model of the disease which is linear,” he explained, and thus fails to take overdiagnosis into account.

Yet worrying about overdiagnosis does not help the treatment of individual patients, interventionists say. As one radiologist put it, “the problem with the whole concept of overdiagnosis is that we have no way of knowing which cancer that we diagnose will or will not kill the patient.” Therefore, the concept is “just theoretical” and ought not be given much weight in cancer detection and treatment. Interventionists also say it is more urgent to focus on the risk of underdiagnosis, or a failure to detect a patient’s illness. False positives may not be a pleasant experience, but as one family medicine doctor put it, “I think it’s a more acceptable consequence than having more women die.”

Despite decades of research, interventionists and skeptics are unable to come to agreement on mammography. More data alone will not change the fundamental fault lines of this disagreement, and the perennial debates about whether to screen women in their forties do not get at the heart of the conflict.

Short of a paradigm-breaking scientific discovery that forces both sides to contend with the limitations of their prior views, our best hope of finding a way past this stalemate and developing a new approach to screening is a deeper sociological examination of how ingrained beliefs about early detection and the benefits and harms of screening restrict how experts, and all of us, really, are able to think about mammography.

Asia Friedman is an associate professor of sociology at University of Delaware and the author of the book “Mammography Wars: Analyzing Attention in Cultural and Medical Disputes” (Rutgers).