Schedule timing of breast cancer screening in women over 50 with risk, age, and breast density

Scheduling breast cancer screening based on risk, age, and breast density in women over 50 years old may be beneficial. Researchers found that screening every 3 years in women with average-risk for breast cancer and lower breast density may be of more benefit, while in those who are at higher relative risk and those with dense breasts, an annual screening schedule may be better, according to a study published in the journal Annals of Internal Medicine.

“For average-risk women in low-density subgroups, which comprise a large proportion of the population, triennial screening provides a reasonable balance of benefits and harms and is cost-effective. Annual screening has a favorable balance of benefits and harms and would be considered cost-effective for subgroups of women aged 50 years with risk levels that are 2 to 4 times the average and that have heterogeneously or extremely dense breasts,” wrote these researchers from the Cancer Intervention and Surveillance Modeling Network.

In collaboration with the Breast Cancer Surveillance Consortium (BCSC), they sought to determine whether a tailored screening approach could provide more benefit that the biennial screening that is generally recommended for women of average-risk for breast cancer who are aged 50 to 74 years old.

To do so, they assessed outcomes of various mammography screening intervals in subgroups of women based on age, risk, and breast density in a cohort of women born in 1970 and followed until death. Using three well-established models, they projected outcomes for women aged 50 years or older in deciding to start or continue biennial screening until age 74, or to change to annual or triennial screenings.

Women were divided into subgroups according to age (50 to 74 years old and 65 to 74 years old), relative risk level (1.0, 1.3, 2.0, 4.0), and four breast density levels (almost entirely fatty, scattered fibroglandular density, heterogeneously dense, and extremely dense). Primary outcomes included lifetime benefit and harm, and secondary outcomes included the use of services and costs. Benefits were comprised of the number of breast cancer deaths averted, and life-years and quality-adjusted life-years (QALYs) gained. Harms included false-positive mammograms, benign biopsies, and overdiagnosis.

In all three models, results showed that screening versus no screening had a greater absolute benefit in the number of deaths averted, life-years gains, and QALYs gained in women with dense breasts and in women at a higher relative risk within each breast density group.

Researchers found that in average-risk women with lower breast density, screening intervals could be safely and effectively extended to once every 3 years. Doing so would reduce false-positive, biopsies, and overdiagnosis, with a minimal effect on the number of deaths from breast cancer that were averted. In women with a higher-risk and with dense breasts, annual screening would be of greatest benefit.

Screening benefits and overdiagnosis increased with breast density and relative risk, while false-positives and benign biopsy results decreased with increasing age.

In women with fatty breasts or scattered fibroglandular density and a relative risk of 1.0 or 1.3, the number of breast cancer deaths averted were similar for triennial and biennial screening in the 50-to-74-year-old age group (median: 3.4 to 5.1 vs 4.1 to 6.5 deaths averted, respectively) and in the 65-to-74-year-old age group (median: 1.5 to 2.1 vs 1.8 to 2.6).

The number of deaths averted from breast cancer increased with annual versus biennial screening in women aged 50 to 74 years with a relative risk of 4.0 at all levels of breast density. This was also true for those aged 65 to 74 years, who had heterogeneously or extremely dense breasts and a relative risk of 4.0. But the harms in this latter group were almost 2-fold greater.

Finally, researchers found that triennial screening for the average-risk subgroup and annual screening for the highest-risk subgroup amounted to less than $100,000 per QALY gained.

“Overall, this comparative modeling study illustrates consistent patterns in benefits and harms that could be useful for guiding shared decision making and tailoring screening intervals. The results show that for all screening intervals, benefits and harms change with risk and breast density. Furthermore, the threshold to decide on the screening interval will depend on individual preference. Assessing breast density and breast cancer risk can identify subgroups of average-risk women with low breast density who can consider triennial screening and higher-risk women with high breast density who may benefit from annual screening,” concluded these authors.

In an editorial accompanying these results, Christine D. Berg, MD, Johns Hopkins Medicine, Bethesda, Maryland, noted that as personalized medical interventions become the norm, including screening for breast cancer, tailoring recommendations based on individual risk and harm profiles is even more important.

In conclusion, she noted: “The USPSTF made a grade B recommendation for biennial mammography screening in average-risk women aged 50 to 74 years. This current work from the well-regarded Cancer Intervention and Surveillance Modeling Network and BCSC investigators helps women and clinicians to possibly individualize screening frequency based on risk and BI-RADS categories. It will be important to track outcomes in women who undergo alternative screening frequencies to validate this approach.”

This study was funded by the National Cancer Institute.