Longitudinal analysis of change in mammographic density in each breast and its association with breast cancer risk

Although breast density is an established risk factor for breast cancer, longitudinal changes in breast density have not been extensively studied to determine whether this factor is associated with breast cancer risk. A nested case-control study at the University of Washington in St.Louis (MO) included women free from cancer at entry who underwent routine screening digital mammography every 1 to 2 years, providing a measure of breast density over the course of up to 10 years of follow-up. A decrease in breast density was observed in all women regardless of subsequent breast cancer development. The rate of density change was significantly slower in the breast in which cancer was later diagnosed. The authors conclude that evaluating longitudinal changes in breast density from digital mammograms may offer an additional tool for assessing risk of breast cancer.