Breast cancer screening for women over 70 is not without risks, according to new research from Yale School of Medicine’s COPPER Center. Although some guidelines recommend continuing screening for older women, a new study emphasizes the importance of assessing potential harms associated with testing, such as overdiagnosis, which, researchers say, can negatively affect quality of life. The findings were published in Annals of Internal Medicine.

“The goal of this work was to quantify the risk of overdiagnosis associated with screening mammography among older women,” says first author of the paper, Ilana Richman, MD, MHS, assistant professor of medicine (general medicine) at Yale School of Medicine and member of Yale Cancer Center. 

“Overdiagnosis refers to a phenomenon where we find breast cancers through screening that never would have caused symptoms. Overdiagnosis can occur when cancers grow very slowly or if a person’s life expectancy is short. Finding these breast cancers can lead to worry and can result in intensive treatments, without improving length or quality of life,” Richman says. “The findings from this study emphasize the need for a careful evaluation of the benefits and harms of screening older women.”

The study included 54,635 women who had no previous history of breast cancer and had recently undergone screening. The researchers compared the cumulative incidence of breast cancer between women who continued screening and those who did not. The analysis used data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Medicare Registry.

Among women aged 70 to 74 years, the researchers found that about six out of every 100 women who had received regular mammography screening were diagnosed with breast cancer, compared to about four cases per 100 unscreened women. This higher rate of breast cancer diagnosis among screened women suggests that a substantial proportion of breast cancers identified through screening in older women did not cause symptoms or otherwise show up in unscreened women. Study authors estimated that about 31% of breast cancer cases among screened women aged 70 to 74 would likely not cause any symptoms or harm.

The study further revealed that 47% of breast cancer diagnoses in women 75 to 84 and 54% of diagnoses in women aged 85 and older were overdiagnosed, meaning that these cancers were unlikely to have become symptomatic or caused health problems. The study did not show statistically significant reductions in the risk of dying of breast cancer among women who were screened.

“While our study focused on overdiagnosis, it is important to acknowledge that overdiagnosis is just one of many considerations when deciding whether to continue screening,” Richman says. “A patient’s preferences and values, personal risk factors, and the overall balance of risks and benefits from screening are also important to take into account when making screening decisions.”