Overdiagnosis from screening mammograms in women over 70 could lead to unnecessary worry and treatments.

Screening mammograms may lead many American women older than 70 to be over-diagnosed with breast cancer, and receive unnecessary tests and treatments as a result, a new study suggests.

Patients are considered over-diagnosed when screening mammograms identify breast cancers that never would have caused symptoms, said the lead study author, Ilana Richman, MD, an assistant professor at Yale School of Medicine and a member of Yale Cancer Center in New Haven, Connecticut, in a statement. This typically happens when cancer grows very slowly, Dr. Richman added.

“Finding these breast cancers can lead to worry and can result in intensive treatments, without improving length or quality of life,” Richman said.

“The findings from this study emphasise the need for a careful evaluation of the benefits and harms of screening older women.”


For the study, researchers examined data on more than 54,000 women 70 and older who had recently received screening mammograms. Among women 70 to 74 years old who continued to get screened, 6 in 100 were diagnosed with breast cancer, compared with 4 in 100 women who stopped getting mammograms.

On the basis of this difference in diagnosis rates, researchers estimated that roughly 31 percent of breast cancer cases identified through screening mammograms were likely an over-diagnosis, according to study results published in the Annals of Internal Medicine.

Over-diagnosis may also become more common in women who continue with screening mammograms even longer. Researchers estimated that about 47 percent of cases identified when women 75 to 84 years old were screened amounted to an over-diagnosis, as were 54 percent of cases caught during screening of women over 85.


This is to be expected for two reasons, says Karsten Juhl Jørgensen, DMedSci, a breast cancer researcher, professor, and chief physician for Cochrane Denmark and the University of Southern Denmark, who wasn’t involved in the new study.

“Older women tend to have slow-growing cancers, so there is more time for competing illnesses to develop and cause death in the time interval between when a cancer can be detected by screening and the time when it causes symptoms,” Dr. Jørgensen says.

At the same time, older women are more likely to have other chronic medical issues, and more likely to die of a wide variety of causes unrelated to cancer, Jørgensen adds. “If a woman dies from another disease, in the increasingly long interval between when a cancer can be detected by screening and when it can be detected because of symptoms, she has been over-diagnosed.”


With so many potential competing causes of death, it’s often possible that a woman diagnosed with breast cancer based on a screening mammogram at age 75 might have a tumour that will kill her only if she lives well past 100, says Otis Brawley, MD, a professor of oncology and epidemiology at Johns Hopkins University in Baltimore and a co-author of an editorial accompanying the new study.

“It means we need to realise the problem exists and be more discreet about who we work up and treat after screening,” Dr. Brawley says.

“Some doctors and patients simply cannot comprehend that there are cancers that are not an emergency.”

More research is also needed to help clinicians better predict which cancers will be fatal and which ones won’t, Brawley adds.


Screening mammograms are breast X-rays to routinely check for cancer in women who don’t have any symptoms, according to the National Cancer Institute.

These are different from diagnostic mammograms, which are done to check for breast cancer when there’s a lump or other signs or symptoms of cancer.


Current guidelines from the U.S. Preventive Services Task Force recommend that women ages 50 to 74 years old get screening mammograms every two years, and leave the option to start mammography at age 40 up to “individual choice.” Those guidelines, issued in 2016, are in the process of being updated to consider whether screening mammograms should be standard for all women ages 40 to 74.

While guidelines also recommend that the overall health and expected life span of older women be taken into consideration, this doesn’t always work well in practice, because patients and doctors don’t want to talk about life expectancy, says Joann Elmore, MD, MPH, a professor at the David Geffen School of Medicine at the University of California in Los Angeles who wasn’t involved in the new study.

These hard conversations are needed, however, to limit the potential for over-diagnosis with screening mammograms in older women, Dr. Elmore says. This is especially true when women have serious, potentially fatal health issues unrelated to cancer, like kidney failure or severe heart disease, that are expected to cut their life short in the next few years.

“This is a challenging topic and hard to operationaliSe in clinical practice,” Elmore says. “Physicians and patients do not like to think about a timeline for death.”