The updated draft recommendation from the U.S. Preventive Services Task Force that would lower the recommended start age for routine screening mammograms by a decade for all average-risk women is not justified, experts argue in a “dissenting view” published in the New England Journal of Medicine.
The proposed change would affect more than 20 million U.S. women, and it’s “hard to see any potential benefits associated with lowering the starting age,” coauthor Steven Woloshin, MD, with Dartmouth Cancer Center, Lebanon, N.H., said in an NEJM podcast.
Back in May, when USPSTF released the draft recommendation, task force member John Wong, MD, with Tufts Medical Center, Boston, said in an interview, “It is now clear that screening every other year starting at age 40 has the potential to save about 20% more lives among all women.”
But, according to Dr. Woloshin, there is no recent evidence that mortality from breast cancer is increasing in young women.
In fact, the United States has seen a steady decrease in breast cancer mortality, especially among younger women. Breast cancer mortality among women under 50 “has been cut in half over the past 30 years,” Dr. Woloshin and coauthors explained.
Another wrinkle: The task force did not base its recent recommendation on randomized trial data. In fact, there have been no new randomized trials of screening mammography for women in their 40s since 2016. Instead, the task force relied on statistical models to “estimate what might happen if the starting age were lowered,” Dr. Woloshin and colleagues said.
Relying on a statistical model, however, “is problematic because it has some very optimistic assumptions about the benefit of mammography,” Dr. Woloshin said in the podcast. For instance, the models assume that screening mammography reduces breast cancer mortality by about 25%.
That 25% reduction is “far greater than what’s reported in the meta-analyses of the available randomized trials,” Dr. Woloshin explained. The meta-analyses report about a 16% reduction for all the trials combined and an estimated 13% for trials at low risk of bias. But “even these meta-analyses are likely to overstate the effect of screening since the trials were done before the major advances in treatment.”
In their own calculations, Dr. Woloshin and colleagues found that lowering the screening age to 40 came with a small potential benefit and a substantial risk for harm.
Combing data from the National Cancer Institute, the team reported that the risk for death for women in their 40s from any cause over the next 10 years was about 3% whether or not they received their biennial mammogram.
The risk for death from breast cancer in that time was 0.23% with mammograms – about 2 in every 1,000 women – and 0.31% without. “That’s 1 less breast cancer death per 1,000 women screened for 10 years,” Dr. Woloshin said.
Put another way, with mammography screening, “the chance of not dying from breast cancer over the next 10 years increases from 99.7% to 99.8%,” Dr. Woloshin said.
The benefit is arguably small, while the harms appear quite significant, Dr. Woloshin said. About 36% of women who begin screening at age 40 would have at least one false alarm over 10 years, and almost 7% would have a false alarm requiring a biopsy in that time frame.