Screening based on breast density at age 40 may reduce breast cancer mortality

A mammography screening strategy based on a baseline breast density measure at age 40 years may be the most effective and cost-effective way to reduce breast cancer mortality, a microsimulation modeling study found.

Researchers used Surveillance, Epidemiology, and End Results–Medicare data to model health outcomes and cost-effectiveness of seven breast cancer screening strategies: no screening, biennial screening from ages 50 to 75 years, triennial screening from ages 50 to 75 years, and four density-stratified strategies (two with baseline mammogram at age 40 years and two with a baseline at age 50 years). The density-stratified strategies assigned annual screening to women with dense breasts and biennial or triennial screening starting at age 50 years for women without dense breasts. Results were published Feb. 9 by Annals of Internal Medicine.

The model suggested that the strategy with a baseline breast density assessment at age 40 years, followed by annual screening from ages 40 to 75 years for women with dense breasts and biennial screening from ages 50 to 75 years for women without dense breasts, had the greatest reduction in breast cancer mortality. It was also associated with more mammograms and higher rates of false positives and overdiagnosis than the other strategies. A cost-effectiveness analysis showed that, compared to biennial screening for all women from ages 50 to 75 years, the previously described density-stratified strategy had an incremental cost-effectiveness ratio of about $36,000 per quality-adjusted life year.

“Baseline screening at age 40 years also offers a ‘teachable moment’ to educate women about breast density and discuss preventive strategies (such as more frequent screening or lifestyle modifications) to mitigate breast cancer risk,” the authors wrote. “Knowledge gained from these discussions can potentially alleviate women's anxiety when receiving their breast density notification, which became a federal requirement on 15 February 2019.”

An editorial stated that several aspects of the results are surprising and inconsistent with prior studies. Annual screening typically results in a higher ratio of harms to benefits because few deaths are averted compared with biennial screening, the authors said. Since this strategy would result in annual screening for 60% of women, the editorial expressed doubt that it could be cost-effective. The study makes possibly overly optimistic assumptions in its models, such as the number of deaths averted, according to the editorial.

An attractive alternative is to focus on overall risk to select screening strategies, rather than just on breast density, because this approach better balances the benefits and harms of screening, the editorial concluded. Breast density is an important risk factor, the editorialists said. “However, we argue that breast density should be combined with age and other risk factors when developing risk-based screening strategies that optimize benefits and minimize harms,” they wrote. The editorialists noted that they support screening biennially from ages 50 to 74 years.