On May 9, the United States Preventive Services Task Force (USPSTF) released updated draft recommendations for breast cancer screening. In contrast to their prior recommendations that most women start screening at 50, the USPSTF — a major national body making preventive care recommendations — now recommends screening mammography every two years for all women ages 40 to 74 years.
This is the USPSTF’s first substantial change to its breast cancer screening recommendations since 2009. Until then, the USPSTF had recommended annual mammography starting at 40. In 2009 and 2016, in light of growing evidence of the harms of mammography screening and the limited benefits among average-risk individuals under 50, the USPSTF recommended screening every two years starting at 50. They emphasized that decisions about starting mammography before age 50 or screening more than every two years should be informed by discussions between patients and their clinicians about mammography’s benefits and harms. In practice, there was growing emphasis on individualizing screening based on patients’ breast cancer risk factors and their own values and preferences about screening.
The USPSTF’s new recommendations shift away from an individualized approach to mammography decisions and are intended to maximize lives saved while helping to address inequities in care and outcomes for historically marginalized individuals, particularly Black women.
But as primary care physicians who have researched mammography use, we are uncertain if they will achieve that goal. Starting mammography at 40 is appropriate for many individuals, but 50 may be right for those who are lower-risk — and all patients should have the opportunity to understand mammography’s limitations as well as its benefits.
Since 2016, the evidence about the benefits and harms of mammography has changed little. There are no new randomized clinical trials, while a limited number of studies provide some additional insights about mammography in older women and the benefits/harms of more- or less-frequent mammograms. The USPSTF also reviewed several studies assessing digital mammography and digital breast tomosynthesis (often called “3D mammography,” a technology increasingly offered at U.S. hospitals), which have improved the ability to detect cancers relative to conventional film mammography. In addition, they considered recent epidemiological data showing increasing incidence of breast cancer among people in their 40s. This increased risk translates to greater screening benefits in this age group than those estimated in 2016.
Another important change is that the USPSTF has adopted an intentional focus on health equity in its processes. In the current update, the USPSTF examined modeling studies that assessed the benefits and harms of mammography screening in the average-risk population of U.S. women overall and for Black women, in particular. Since Black women are more likely to die of breast cancer than white women — mortality rates are 40% higher — they may experience a more favorable benefit/harm ratio from screening. Black women also have higher breast cancer incidence in their 40s than white women. Some authors have argued for different screening approaches for Black women in light of these inequities in outcomes.
The modeling report accompanying the USPSTF recommendations found that mammography screening every two years starting at age 40 saves more lives than starting at age 50 but leads to more false positive tests, unnecessary biopsies, and overdiagnosed cancers (cancers that would never become clinically evident in a woman’s lifetime in the absence of screening).
Because the incidence of breast cancer is rising among all women and because young Black women have higher risks of cancer than young white women and higher risks of breast cancer death at any age, the USPSTF now perceived the relative benefits to harm ratio of initiating mammography at 40 as more favorable than in 2016. Across all women, the models estimated that screening every two years between ages 50-74 years averted 7.1 breast cancer deaths per 1,000 people screened. Among Black women, screening every two years between ages 50-74 averted 10.1 breast cancer deaths per 1,000 persons screened. For both groups, about one to two additional deaths per 1,000 were averted if the starting age was 40 instead of 50 years.
The harms of mammography are common: Among 1,000 people screened with digital mammography over a lifetime, there would be 1,021 false positive tests, 148 unnecessary biopsies, and 10 overdiagnosed cancers. Annual mammography results in substantially more mammograms, and more false positives, unnecessary biopsies, and overdiagnosis and only a small increase in the number of breast cancer deaths averted compared with mammograms every two years. That’s why the USPSTF recommends mammograms every two years.
The USPSTF’s emphasis on health equity is important and overdue. Even though racial categorizations are highly problematic in medical research, there remains value in explicitly examining outcomes stratified by race and considering public health recommendations that could reduce disparities. Recommendations based only on benefits and harms averaged across populations could worsen existing gaps between advantaged and historically marginalized groups.
Some experts argue that a lower “default” screening age could have particular value for patients at high risk for poor outcomes such as Black women. This could be especially true if a higher proportion of Black women are cared for in settings where individualized risk assessment and shared decision-making do not routinely occur, or if clinicians are less likely to engage in risk assessment with their Black patients relative to their white patients, as some studies suggest. However, Black women are often diagnosed with faster-growing breast cancers, raising the possibility that annual screening may be a more effective strategy than every-two-year mammograms and that individualized approaches remain important to consider.
Despite the USPSTF’s good intentions, there are important limitations to the concept that lowering recommended screening ages will improve equity. First (as the authors of the supporting research note), on its own, earlier screening is unlikely to have a major impact on the racial and ethnic inequities in the U.S.’s breast cancer outcomes. Black women receive inferior care at many points in the breast cancer diagnosis and treatment continuum — for example, lower mammogram quality, longer delays following abnormal mammograms and less receipt of guideline-concordant treatment. Lower screening rates have not been identified as a major contributor to disparities in outcomes. Thus, discussions about screening initiation must not divert attention or resources from interventions to address the structural racism that leads to inadequate care and unacceptable racial differences in breast cancer mortality.
Second, while mammography is the only breast cancer screening test that has been shown to lower breast cancer mortality, the USPSTF’s 2023 evidence review continues to demonstrate that it provides only modest benefits, especially for younger women, and real harms, particularly overdiagnosis which subjects people to unnecessary cancer treatment. All patients need to be aware of the low likelihood that a mammogram will avert a breast cancer death, and the moderate likelihood that they will experience a false positive result or overdiagnosis over years of regular screening.
We hope that despite the new recommendations, clinicians will continue to incorporate cancer risk-assessment and individualizing decisions about screening in their practices. This is important to identify individuals who may benefit from enhanced screening (e.g., annual mammography), as well as women for whom screening later or less often is reasonable based on their risk profile or their values and preferences. Clinicians also should continue to engage in shared decisions to help patients understand mammography’s benefits and harms and prepare for the likelihood of outcomes such as false positives. All patients deserve these discussions. Abundant evidence (including that cited by the USPSTF) supports the value of an individualized approach to mammography.
The USPSTF draft recommendation has many worthy aspects, particularly its highlighting of inequities in breast cancer outcomes in the United States, which require urgent intervention. However, it is not clear that returning to a one-size-fits all approach to screening will result in better outcomes for patients.
Lydia E. Pace, M.D., MPH, is a primary care physician at Brigham and Women’s Hospital and associate professor of medicine at Harvard Medical School. Nancy L. Keating, M.D., MPH, is a primary care physician at Brigham and Women’s Hospital and a professor of health care policy and medicine in the Department of Health Care Policy at Harvard Medical School.