The National Breast Cancer Coalition calls for proven evidence-based strategies to answer tough questions and save lives.
Mammography screening is, by definition, something for women with no symptoms or signs of breast cancer. And when screening asymptomatic women for breast cancer, the benefits must be clear and the harms nonexistent. Unfortunately, the United States Preventive Services Task Force’s (USPSTF) draft recommendations for breast cancer screening for women at average risk do not meet those standards.
Screenings should ultimately result in fewer deaths. But whether mammography screening reduces deaths, particularly in younger women, has been debated for decades. Researchers have conducted at least seven prospective randomized clinical trials—the gold standard of evidence—and none have resolved the matter.
Now less robust—and less clear—methods of evidence, known as statistical modeling, are being used to find a benefit in early screening. These methods are complex and require many assumptions, yet the USPSTF is using these model outputs to recommend biennial screenings for all women age 40 and over, rather than let women decide for themselves.
Read our official statement on the draft guidelines.
Screening mammography for breast cancer in average-risk women with no symptoms is an extremely complex and controversial topic. Because it takes place in a healthy population, the National Breast Cancer Coalition (NBCC) has long held that the benefits of screening must significantly outweigh the risks.
Under its prior recommendations, which NBCC reluctantly supported, the USPSTF called for biennial screening mammography for women age 50 to 74, with the option for biennial screening among women age 40 to 49 following a conversation with their doctor about the risks and benefits. Women got to choose. These guidelines acknowledged the known harms of screening and that randomized controlled trial data have shown limited benefit for all women, especially in this age group.
No new experimental data have emerged regarding the benefits and harms of screening mammography. So what informed these new recommendations?
The situation is complex and the science is dense. The USPSTF based its recommendations on a collaborative modeling analysis using the six Cancer Intervention and Surveillance Modeling Network (CISNET) breast cancer models.
These six statistical models were used to independently estimate breast cancer outcomes in a hypothetical group of 1,000 average-risk 40-year-old women with and without breast cancer screening (either digital mammography or digital breast tomosynthesis). The USPSTF looked at outcomes for women of all races and Black women, respectively.
The models did not agree. Each modeling approach found different estimates for each outcome and harm. The median value across all models was used to provide the best estimates of benefit and harm in each scenario.
In 2016, using the same statistical modeling approach and the same six CISNET models, the USPSTF gave screening those age 40 to 49 a “C” level recommendation, leaving the decision up to women.
In 2023, the collaborative model analysis raised the strength of the recommendation from a “C” (requiring informed decision) to a “B” (a practice that the provider should strongly encourage, and one they will be graded on). What was the difference? They found an additional 0.3 breast cancer deaths averted per 1,000 women screened over a lifetime.
The USPSTF model estimates include:
Overdiagnosis —and consequently, overtreatment—is a major harm of screening. Detecting, removing, and treating breast cancers that would otherwise never have harmed women does not save lives. But it does subject women to toxic treatments that could lead to significant lifelong health issues, including other cancers.
Until researchers can determine which breast cancers will eventually spread, reduce quality of life, or result in death, overdiagnosis will continue to be a consequence of the current screening technologies.
A key limitation of the modeling approach is that all the models assumed 100-percent screening adherence, prompt evaluation of abnormal screening results, and appropriate and timely access to treatment. Unfortunately, this is not how it works in the real world, so the potential benefits are a best-case, unlikely scenario.
The USPSTF cited epidemiological data that show the incidence rate (the number of new cases) of invasive breast cancer in women age 40 to 49 increased by 2.0 percent annually between 2015 and 2019. But this increase is likely due, in large part, to the extensive screening that already takes place among women in this age group.
According to the Centers for Disease Control and Prevention, from 2008 to 2018, more than 60 percent of all women age 40 to 49 in the United States were screened with mammography within the past two years. That would of course increase the number diagnosed.
It appears that a key impetus for the USPSTF in changing the recommendation is to address the mortality gap between white and Black women. While the goal, of course, is not to have Black women die at the same rate as white women but to eliminate breast cancer mortality for all, we must address this gap.
Despite having a comparable incidence of breast cancer, death from breast cancer is 40 percent higher among Black women. However, it’s not clear how starting breast cancer screening at 40 will have any effect on the mortality gap, particularly given that, as noted above, about 60 percent of women of all races in this age range are already being screened. The gap persists even though Black and white women in this age group are screened at the same rate.
Mammography screening will not eliminate longstanding disparities in breast cancer outcomes regardless of the start and stop age. These disparities are the result of structural racism, and the health care policies that create inequitable access to appropriate, timely, and quality care.
Spending billions more dollars each year on ineffective—or at best, weakly effective—interventions diverts resources from addressing the tough questions, like how to prevent breast cancer or stop it from metastasizing and how to create an equitable health care system.
Mammography screening is not the answer to ending breast cancer and saving lives, and continued emphasis on it as a dominant strategy is misplaced.
