Changes in mammographic density over time and the risk of breast cancer: An observational cohort study

Breast. 2019 Aug;46:108-115. doi: 10.1016/j.breast.2019.04.007. Epub 2019 May 13.


Background: The effect of changes in mammographic density over time on the risk of breast cancer remains inconclusive.

Methods: We used information from four centres of the Breast Cancer Screening Program in Spain in the period 1996-2015. We analysed individual level data from 117,388 women first screened age 50-54, with at least two screening examinations. Breast density was determined using the BI-RADS classification (A to D in increasing order) at earliest and latest screening examination. Adjusted Poisson regression models were used to estimate the relative risk (RR) and 95% confidence intervals (95%CI) of the association between changes in mammographic density and breast cancer risk over time.

Results: During an average 5.8 years of follow-up, 1592 (1.36%) women had a breast cancer diagnosis. An increase in density category increased breast cancer risk, and a decrease in density decreased the risk, compared with women who remained in the same BI-RADS category. Women whose density category increased from B to C or B to D had a RR of 1.55 (95%CI = 1.24-1.94) and 2.32 (95%CI = 1.48-3.63), respectively. The RR for women whose density increased from C to D was 1.51 (95%CI = 1.03-2.22). Changes in BI-RADS density were similarly associated with the risk for invasive cancer than for ductal carcinoma in situ.

Conclusions: Although a modest proportion of women changed BI-RADS density category, mammographic density changes modulated the risk of breast cancer and identified women at a differential risk. Using two longitudinal measures of BI-RADS density could help target women for risk-based screening strategies.

Keywords: Breast neoplasms; Longitudinal studies; Mammographic density; Mass screening.

Publication types

  • Observational Study

MeSH terms

  • Aged
  • Breast / diagnostic imaging
  • Breast / pathology
  • Breast Density*
  • Breast Neoplasms / diagnosis
  • Breast Neoplasms / epidemiology
  • Breast Neoplasms / etiology*
  • Early Detection of Cancer / methods
  • Early Detection of Cancer / statistics & numerical data*
  • Female
  • Humans
  • Mammography / statistics & numerical data*
  • Middle Aged
  • Risk Assessment
  • Risk Factors
  • Spain / epidemiology
  • Time Factors*