Changes in mammographic density over time in breast cancer cases and women at high risk for breast cancer

Abstract

High mammographic breast density is one of the strongest intermediate markers of breast cancer risk, and decreases in density over time have been associated with decreases in breast cancer risk. Using repeated measures of mammographic density in a cohort of high-risk women, the Women at Risk (WAR) cohort at Columbia University Medical Center (N = 2670), we examined whether changes in prediagnostic mammographic density differed among 85 prospectively-ascertained breast cancer cases and 85 age-matched controls, using a nested case-control design. Median age at first mammogram was 51 years (range, 29-77 years), with a median of 4 years between first and second prediagnostic mammogram (range, 1-15 years). Using linear regression with change in percent density as the outcome, we found that in women who did not go on to be diagnosed with breast cancer, change in percent density decreased as time between first and second mammogram increased (β = -1.62% per year, p = 0.004). However, in women who did go on to be diagnosed with breast cancer, there was no overall change in percent density associated with time between first and second mammogram (β = 0.29% per year, p = 0.61); the change over time was statistically significantly different between cases versus controls (p <0.009). If replicated in larger cohorts, these results suggest that within-individual changes in mammographic density as measured by percent density may be a useful biomarker of breast cancer risk. What's New? Higher breast density means a higher risk of cancer. This is well known, but only for single measure of breast density. As a woman ages, her breasts become less dense, and how might these changes over time affect cancer risk? These authors tackled that question by analyzing mammographic data on women at high risk of breast cancer. They found that breast density decreased in women who did not develop cancer, but not in those who did, suggesting that monitoring changes in breast density could help identify women at greater risk of disease. © 2014 UICC.