Breast cancer risk particularly increased with estrogen plus progestin
Karla Kerlikowske, M.D., of the California Pacific Medical Center Research Institute in San Francisco, and colleagues evaluated data on 587,369 women who underwent 1,349,027 screening mammography exams. Breast cancer was diagnosed among 14,090 women. The researchers used a survival model to determine five-year breast cancer risk for subgroups of women classified by their Breast Imaging Reporting and Data System (BIRADS) breast density, menopausal status, age, and current hormone therapy use, assuming a body mass index of 25 kg/m².
The researchers found that, among women aged 55 to 59 years with low breast density (BIRADS-1), the five-year breast cancer risk was 0.8 percent for those not using hormone therapy and 0.9 percent for those using estrogen and estrogen plus progestin. Among women aged 55 to 59 years with very high breast density (BIRADS-4), the five-year breast cancer risk was 2.4 percent for those not using hormone therapy, 3.0 percent for those using estrogen, and 4.2 percent for those using estrogen plus progestin. Compared to those with average breast density (BIRADS-2), risk of advanced-stage breast cancer was 1.7-fold higher for postmenopausal women using hormone therapy who had BIRADS-4.
"Approximately 50 percent of postmenopausal women have high or very high breast density, are at high breast cancer risk, and may be considering or using hormone therapy. Postmenopausal women with high breast density may want to consider the added risk of breast cancer when deciding on whether to start or stop hormone therapy, especially estrogen plus progestin," the authors conclude.
One author disclosed financial ties to Eli Lilly.
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