The U.S. Preventive Services Task Force—a volunteer panel of national experts in prevention and evidence-based medicine that makes recommendations for clinical preventive services such as screenings, counseling services, or medications—has generally been considered an honest broker, willing to buck political and popular pressures to give advice consistent with the available evidence. New USPSTF draft recommendations on breast-cancer screening suggest that this may have changed.
When the USPSTF last updated its breast-cancer screening recommendations about eight years ago, it found that, for women under 50 with an average risk of cancer, the harms of screening outweighed the benefits. It recommended routine screening for women 50 or older and advised younger women to consult with their physicians to discuss whether their history and individual risk factors warrant screening.
This recommendation echoed guidelines used around the world. The U.K, France, Denmark, and Germany, for example, screen women 50 and older, but there is no organized screening of women in their forties. Switzerland has no screening program for women of any age.
The USPSTF recently issued a draft recommendation lowering the starting age for mammography screening from 50 to 40 years. This will affect approximately 20 million additional women. It is not clear what prompted the change.
The USPSTF acknowledged that no new randomized trials of screening mammography for women in their forties have been conducted since the previous recommendation was made. Nor have new, follow-up findings emerged from the eight previous randomized trials in this age group, all of which found no significant benefit.
Instead, the task force relied on modeling studies to provide information about the benefits and harms of breast-cancer screening in different age groups. As with any model, the results depend on the assumptions made. The model assumed that screening mammography reduces breast-cancer mortality by 25 percent and concluded that lowering the starting age from 50 to 40 would result in 1.3 fewer deaths over a lifetime for every 1,000 women screened.
The 25 percent risk-reduction figure is almost certainly too optimistic. The randomized studies showed only a 16 percent relative risk reduction in this age group. But even if we accept this optimistic risk-reduction figure, the benefit is small. The risk of breast cancer for women in their forties is already low. Incidence starts to rise steeply at age 50. Eighty-three percent of breast cancers occur among women aged 50 and older, and 91 percent of deaths from breast cancer occur in this age group.
Breast-cancer mortality in the United States has steadily declined over the past 30 years. Women aged 40 to 49, who already had mortality rates less than half those of women 50 and older, experienced the most pronounced mortality decline, with rates falling by half. Similar patterns have occurred in other developed countries, including ones where screening is rare at any age—suggesting that declining mortality more likely resulted from improved treatment rather than screening.
Averting 1.3 deaths per 1,000 women over their lifetimes by initiating screening at age 40 rather than 50 amounts to improving these women’s chances of not dying from breast cancer by a little more than one-tenth of 1 percent.
This small gain, however, comes at a high cost. Mammogram screening has a significantly higher rate of false positives for women in their forties than for older women. The USPSTF model estimates that lowering the age for initiating screening from 50 to 40 will result in about a 60 percent increase in false positives. That adds up to more than 500 false-positive results over ten years for every 1,000 women who begin biennial mammography screening at 40, leading to psychological harm, as well as additional testing and invasive procedures, such as biopsies, which bring no benefit.
Changing the starting date will also lead to more cases of overdiagnosis: finding early forms of cancer such as non-invasive disease or very early invasive disease that would never have become clinically apparent or affected the woman’s life expectancy. Randomized trials estimate that 11 percent to 22 percent of mammographically detected cancers are over-diagnosed. Once uncovered, these cancers are treated unnecessarily with surgery, radiation, and chemotherapy—all causing side effects. Such women are left psychologically traumatized by the misleading diagnosis of a life-threatening disease.
In other words, recommendations to start screening at 40 may harm some of the women that screenings are meant to help and waste billions of dollars. Quantifying the cost is difficult, especially for women in their forties. The best-known study found that overdiagnosis and false positives in women aged 40 to 59 costs an estimated $4 billion per year—roughly half of the annual expenditure on mammography screening. The costs will be lower for women in their forties than for the larger group as a whole but would likely still be substantial. Whatever the actual cost, it must be balanced against the clearly lower benefit of screening women in their forties compared with older women.
If the cost-benefit calculation for screening has not clearly changed, why did the task force change its recommendations? A clue is found in the introduction to the modeling study performed for the task force, which noted, “The USPSTF has recently highlighted the need to include ‘an intentional focus on embedding health equity’ into its processes.” The introduction cited “New and more inclusive science about breast cancer in people younger than 50.” In the next paragraph, it noted “Black women are 40 percent more likely to die of breast cancer than White women and too often get deadly cancers at younger ages.” It described this disparity as an “inequity.”
The choice of words is telling. Rather than describing the higher incidence of deadlier, more aggressive cancers in younger black women as an inequality—suggesting a biologically determined difference between individuals or population groups—the task force used inequity, which suggests a lack of fairness or justice. The task force went on to emphasize the importance of addressing “the health disparities faced by Black, Hispanic, Latina, Asian, Native American, and Alaska Native women,” and of the potential for timely treatment “to save more lives for people experiencing disparities related to racism.”
Black women are twice as likely as other women to be diagnosed with the deadliest form of breast cancer: triple negative tumors. Triple-negative breast cancers are more aggressive, have a higher risk of spread, fewer treatment options, and higher mortality rates than other types. The higher incidence of triple-negative cancers in black women has nothing to do with systemic racism, however, but with tumor biology determined by genetic factors. White women have, comparatively speaking, a higher percentage of tumors with favorable tumor biology than black women.
Increasing screening for younger black women will not address racism leading to delayed treatment and lower quality of available medical services. It might actually divert resources and attention from those problems. Lowering the age of screening will not eliminate disparities, since the screening rates for black and white women in their forties are already roughly equivalent, and rates for black women aged 50 and over are significantly higher than for all women.
What explains USPSTF’s eagerness to address racial issues? While the USPSTF is presumably an independent, nongovernmental body, it was authorized by Congress in 1984 and is funded, staffed, and appointed by the Department of Health and Human Services’ Agency for Healthcare Research and Quality. It is not immune from the current administration’s fixation on diversity, equity, and inclusion.
Regardless of its motivation, the USPSTF should reconsider its decision to lower the starting age for mammography screening. The task force’s modeling provides insufficient evidence of benefit to overcome the well-known harms of screening younger, average-risk women, and the new recommendations represent a departure from USPSTF’s previous high standards. We should continue to trust younger women, with the assistance of their physicians, to make health decisions in their own best interests.