Postmenopausal women with high breast density are at an increased risk of developing breast cancer, according to the results of a study published in the Journal of Clinical Oncology. This risk increases with the use of postmenopausal hormone therapy.
Breast density refers to the extent of glandular and connective tissue in the breast. Breasts with more glandular and connective tissue—and less fat—are more dense. Women with higher breast density are at increased risk of developing breast cancer. Breast density can be assessed by mammography.
In this study researchers examined the relationship between breast density and breast cancer risk based on menopausal status and the use of postmenopausal hormones (either estrogen alone or estrogen plus progestin). Previous studies have indicated that postmenopausal use of estrogen plus progestin increases the risk of breast cancer.
The researchers collected data on 587,369 women who underwent 1,349,027 screening mammograms. Of these women, 14,090 were diagnosed with breast cancer. The women in the group were categorized by age, menopausal status, current use of postmenopausal hormones, and breast density (using the Breast Imaging Reporting and Data System, or BIRADS, to classify density).
The researchers found that breast cancer risk was low among women with low breast density (BIRADS-1) and higher among women with high breast density (BIRADS-4). The risk increased with use of postmenopausal hormones, especially estrogen plus progestin. The data are outlined in the table below:
Table 1: Five-year risk of breast cancer for women age 55 to 59
No hormone therapy
Estrogen plus Progestin
Low Breast Density (BIRADS-1)
High Breast Density (BIRADS-4)
The risk of developing advanced-stage breast cancer was increased 1.7-fold for postmenopausal women with high density (BIRADS-4) who used postmenopausal hormones compared with their counterparts with average density (BIRADS-2).
The researchers concluded that women with high breast density are at an increased risk of developing breast cancer, especially if they use estrogen plus progestin.
 Kerlikowske K, Cook AJ, Buist DSM, et al. Breast cancer risk by breast density, menopause, and postmenopausal hormone therapy use. Journal of Clinical Oncology [published early online]. July 19, 2010.