A collaborative modeling study evaluating outcomes for various screening intervals for women over the age of 50 based on breast density and risk for breast cancer has found that average-risk women with low breast density undergoing triennial screening and higher-risk women with high breast density receiving annual screening will maintain a similar or better balance of benefits and harms than average-risk women receiving biennial screening. In addition to being cost-effective, limiting the screening intervals to every 3 years for average-risk women with low-breast density could reduce false-positive results, biopsies, and overdiagnosis, with minimal effect on breast cancer deaths averted, according to the study. The findings by Amy Trentham-Dietz, PhD, of the University of Wisconsin School of Medicine and Public Health, Madison, and colleagues could be useful for guiding shared decision-making and tailoring screening intervals. The study was published in Annals of Internal Medicine.
This study included three microsimulation models using national incidence, breast density, and screening performance data. The models included Model E (Erasmus Medical Center in Rotterdam, Netherlands); Model GE (Georgetown University Medical Center in Washington, DC, and Albert Einstein College of Medicine in Bronx, New York); and Model W (University of Wisconsin-Madison in Madison, Wisconsin, and the Harvard Medical School in Boston). The models used a lifetime horizon to evaluate screening strategies for two populations: women aged 50 years who were starting screening for the first time and those aged 65 who had received biennial screening from ages 50 to 64.
Strategies for each age group varied by screening interval (annual, biennial, and triennial) and were compared with no screening. The intervals were applied to the population subgroups based on combinations of four breast density levels: almost entirely fat; scattered fibroglandular density; heterogeneously dense; or extremely dense; and four relative risk levels: 1.0 (average); 1.3 (eg, postmenopausal obesity); 2.0 (eg, history of benign breast biopsy results); and 4.0 (history of lobular carcinoma in situ).
The researchers used lifetime breast cancer deaths, life expectancy and quality-adjusted life years (QALYs), false-positive mammography results, benign biopsy results, overdiagnosis, cost-effectiveness, and ratio of false-positive results to breast cancer deaths averted as measurements.
Study Findings
Screening benefits and overdiagnosis increase with breast density and relative risk. False-positive mammography results and benign results on biopsy decrease with increasing risk. Among women with fatty breasts or scattered fibroglandular density and a relative risk of 1.0 or 1.3, breast cancer deaths averted were similar for triennial vs biennial screening for both age groups (50–74 years, median of 3.4–5.1 vs 4.1–6.5 deaths averted; 65–74 years, median of 1.5–2.1 vs 1.8–2.6 deaths averted).
Breast cancer deaths averted increased with annual vs biennial screening for women aged 50 to 74 years at all levels of breast density and a relative risk of 4.0 and those aged 65 to 74 years with heterogeneously or extremely dense breasts and a relative risk of 4.0. However, harms were almost twofold higher. Triennial screening for the average-risk subgroup and annual screening for the highest-risk subgroup cost 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…. 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 the study authors.
Funding for this study was provided by the National Cancer Institute. ■
Trentham-Dietz A, et al: Ann Intern Med. August 23, 2016 (early release online).
