The New USPSTF Mammography Recommendations — A Dissenting View

“Recently, the U.S. Preventive Services Task Force (USPSTF) changed its recommendation for the starting age for mammography screening from 50 to 40 years. Previously, the Task Force deemed screening in 40-to-50-year-old women a personal choice. Because USPSTF recommendations are so influential, mammography screening for women in their 40s will probably become a health care performance measure; if so, it will effectively become a public health imperative with which primary care practitioners must comply. Such a change will affect more than 20 million U.S. women, and it raises some important questions.

First, is there new evidence that mortality from breast cancer is increasing? To the contrary, there has been a steady decrease in breast-cancer mortality in the United States [..]. The reduction has been most pronounced among women under 50, whose breast-cancer mortality has been cut in half over the past 30 years, according to the National Vital Statistics System. Similar patterns are seen in other high-income countries, including both those where screening of women in their 40s is very rare (Denmark and the United Kingdom) and those where screening is rare in all age groups (Switzerland) — which suggests that the decline has resulted largely from improved treatment, not screening [..].

Second, is there new evidence that the benefit of mammography is increasing? Since the previous USPSTF recommendation was made, there have been no new randomized trials of screening mammography for women in their 40s. Eight randomized trials for this age group, including the most recent (the U.K. Age trial), revealed no significant effect. This finding reflects both the rarity of death related to breast cancer among women in their 40s and the fact that screening reduces mortality less than was hoped — perhaps because more aggressive disease occurs in this age group. Fast-growing cancers are more likely to be missed by screening, often appearing in the interval between exams.

Instead of new trial data, the new recommendation is based on statistical models that estimate what might happen if the starting age were lowered. The models assume that screening mammography reduces breast-cancer mortality by about 25% and conclude that screening 1000 women from 40 to 74 years of age, instead of 50 to 74, would result in one to two fewer breast-cancer deaths over a lifetime.

[..] the modeled 25% relative risk reduction in breast-cancer mortality with mammographic screening exceeds that observed in meta-analyses of the randomized trials: a 16% relative risk reduction for all eight trials combined (95% confidence interval [CI], 27% to 4% reduction) and a 13% relative risk reduction in the three trials with low risk of bias (95% CI, 27% reduction to 3% increase).

[..] For U.S. women in their 40s, the risk of death from any cause in the next 10 years is about 3% regardless of screening. The modeled benefit of mammography is a reduction of a woman’s 10-year risk of death from breast cancer from about 0.3% to about 0.2%, a difference of 0.1 percentage point (one breast-cancer death per 1000 women screened for 10 years). In other words, with screening, the likelihood of not dying from breast cancer in the next 10 years increases from 99.7% to 99.8%.

[..] By far the most common outcomes are false alarms: the USPSTF model estimates that 36% of women 40 to 49 years of age will have at least one in a 10-year course of biennial screening. All will require more testing to prove they don’t have cancer; some will undergo multiple tests and face substantial out-of-pocket costs. And some will experience fear: about a third of women describe the experience as “very scary” or “the scariest time of my life.” [..]

More screening can’t address underlying differences in cancer biology: the incidence of triple-negative breast cancer (which lacks expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2) among Black women is twice that among White women, according to the National Cancer Institute. This subtype is the most aggressive, has the least effective treatments, and is the most likely to be missed by screening.

Nor would earlier screening address the problems facing poor women, who tend to be disproportionately Black, such as the lower quality of medical services available, delayed follow-up on abnormal scans, delays to treatment, and less use of adjuvant therapy. Indeed, lowering the screening age could actually exacerbate the problems contributing to the disparity — by diverting resources toward expanded screening. We need to do more of what really works: ensure that high-quality treatment is more readily accessible to poor women with breast cancer.

A change in mammography recommendations would be supported if there were evidence that breast-cancer outcomes were worsening or if there were new evidence that screening younger women had clear benefits. In fact, neither condition applies.”

Full perspective, S Woloshin, KJ Jorgensen, S Hwang and HG Welch, New England Journal of Medicine, 2023.9.21