As of October 2014, 19 states have enacted laws requiring women to be directly informed if they have dense breasts and would benefit from supplemental screening. However, the recommended type of supplemental screening for women with dense breasts remains unclear. With 15 additional states considering similar laws and federal legislation introduced, physician scientists at the University of Washington and Seattle Cancer Care Alliance (SCCA) investigated the potential impact of supplemental screening for women with dense breast tissue. The study's findings are published this month online in the journal Radiology.
The study found that adding tomosynthesis (3D mammography) to routine biennial digital mammography screening among U.S. women with dense breasts could improve health outcomes at a reasonable cost relative to digital mammography screening alone. This is the first comparative effectiveness study performed at the national level using an established model, and it could influence future screening recommendations for women with dense breast tissue who comprise nearly half of all women in the United States.
"We felt that this analysis would help inform timely policy and practice decisions given both increased attention to screening for women with dense breasts and rapid adoption of tomosynthesis in routine practice," said Christoph I. Lee, M.D., M.S.H.S., lead author of the study, assistant professor in the Department of Radiology and Health Services at the University of Washington and staff radiologist at SCCA. "While screening ultrasound is currently being touted as the additional test of choice for women with dense breasts, it requires significant increases in manpower and leads to a larger number of false positives. Digital breast tomosynthesis, in contrast to ultrasound, offers operational and ease-of-use advantages since it is an integrated part of newer-generation mammography units."
Mammography remains the only screening test proven to decrease mortality from breast cancer. However, mammography is less accurate in women with dense breasts for whom cancers may be masked by overlapping breast tissue. Moreover, dense breasts compared to average-density breasts are associated with a moderate increased relative risk for developing breast cancer independent of the masking effect. Given that nearly half of the U.S. screening population has
dense breasts, an increasingly large number of women may be encouraged to consider supplemental screening beyond conventional mammography.
According to Constance Lehman, M.D., Ph.D., chief of breast imaging at the University of Washington, and director of imaging at Seattle Cancer Care Alliance, "Prior research has reported improved diagnostic accuracy with tomosynthesis, with both fewer false positives and higher cancer detection rates. However, until this study, we had little understanding of the impact of that improved performance on patient outcomes and costs."
For this study, researchers used a breast cancer simulation model previously used to guide the U.S. Preventive Services Task Force recommendations for breast cancer screening. The team estimated the comparative clinical effectiveness and cost effectiveness of biennial screening with both digital mammography and tomosynthesis versus digital mammography alone among U.S. women ages 50 to 74 years with dense breasts, using data and metrics from the National Cancer Institute's Breast Cancer Surveillance Consortium, Medicare reimbursement rates, and medical literature. They found that one breast cancer death would be prevented and 810 false-positive exams avoided per 2,000 women screened over 12 rounds of screening, and that the incremental cost per quality-adjusted life year (QALY) gained by adding tomosynthesis to digital mammography screening was $53,893, well below the established threshold for cost effectiveness ($100,000 per QALY gained).
"The population outcomes we report show the promise of tomosynthesis, but it is critical to emphasize the need for primary data on tomosynthesis performance in U.S. community settings," said Anna Tosteson, Sc.D., a co-author and James J. Carroll Professor at the Geisel School of Medicine at Dartmouth. "As such evidence becomes available, population modeling will be needed to elucidate the most clinically effective and efficient approaches to screening women with mammographically dense breast tissue."
The study team currently uses effectiveness data from European trials to estimate the effects of adding tomosynthesis among the U.S. population. "While this modeling study suggests that there is a high likelihood that breast tomosynthesis will be cost-effective in the U.S., further primary data from ongoing and planned studies will be very important to reduce uncertainty regarding the model estimates, " said Scott Ramsey, M.D., Ph.D., another study co-author and co-director of the Hutchinson Institute for Cancer Outcomes Research.
"Overall, this study provides women, physicians, payers and policymakers in the U.S. with much needed information regarding the balance between potential benefits and harms of combined mammography and tomosynthesis screening for women with dense breast tissue," Dr. Lee said.
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