Should Breast Density At Age 40 Guide Mammography Screening Strategy?

A breast cancer screening strategy based on a single measure of breast density obtained at age 40 may a cost-effective way to reduce deaths from breast cancer, researchers propose in a paper in Annals of Internal Medicine.

Current breast cancer screening recommendations advise starting mammography at age 50 for women at average risk. But women with dense breasts are at increased risk for breast cancer and might benefit more than other women from earlier and more frequent screening mammography, Dr. Ya-Chen Tina Shih, with University of Texas MD Anderson Cancer Center in Houston and colleagues point out.

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Using a microsimulation model, they compared health outcomes and cost-effectiveness of seven breast cancer screening strategies: no screening, biennial screening between age 50 and 75, triennial screening between 50 and 75, and four breast density-stratified strategies (two with baseline mammogram at age 40, and the other two at age 50). All four density-stratified strategies assigned annual screening to women with dense breasts, and biennial or triennial starting at age 50 for women without dense breasts.

Among all seven strategies, the researchers found that the most cost-effective is the density-stratified strategy with universal baseline mammography screening at age 40, then annual screening for women with dense breasts from age 40-75 and biennial screening for women without dense breasts from age 50-75 years.

This strategy resulted in the most deaths averted but was also associated with a larger number of lifetime mammograms and higher rates of false positives and over diagnosis, Dr. Shih and colleagues note. Still, this strategy was cost-effective, with an incremental cost-effectiveness ratio (ICER) of about $36,000 per quality-adjusted life year (QALY), which is considered cost-effective, they point out.

In email to Reuters Health, Dr. Shih said this analysis was prompted by "increasing attention on breast density. Many states and now federal government require providers to inform women about their breast density. And some risk calculators available online (e.g., Breast Cancer Surveillance Consortium Risk Factor) include breast density as one of the risk factors. But many women won't know their density classification until age 50. Guidelines do leave screening decision for women in their 40s to 'personal preference,' which is rather vague."

"The take home message," said Dr. Shih, "is that a baseline density screening at age 40 is worth considering for women at average risk for breast cancer. What my coauthors and I hope to achieve is to start the conversation about the idea of baseline density assessment at age 40. We hope this will inspire researchers/policy makers to build on this concept to design screening strategies that will be even more cost-effective than the strategy proposed in our study (e.g., a further stratification between women with heterogenous and extremely dense breasts) and also invite discussions on how to use baseline density assessment at age 40 as an opportunity to connect women with healthcare system when they reach age 40 and explore possibilities to expand the baseline assessment from mammography to other health assessments."

Weighing in on this research in a linked editorial, Dr. Karla Kerlikowske and Dr. Kristen Bibbins-Domingo, with University of California San Francisco, say, "Breast density is an important risk factor to include in risk-based screening strategies because it is both a strong and prevalent risk factor accounting for a large proportion of breast cancers. 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. We believe that until a more robust risk-based strategy is identified, the frontier curves presented in Shih and colleagues' analyses support screening biennially from ages 50 to 74 years."

—Megan Brooks

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