Mammographic Density Changes over Time and Breast Cancer Risk: A Systematic Review and Meta-Analysis

Abstract

The aim of this meta-analysis was to evaluate the association between mammographic density changes over time and the risk of breast cancer. We performed a systematic literature review based on the PubMed and ISI Web of Knowledge databases. A meta-analysis was conducted by computing extracted hazard ratios (HRs) and 95% confidence intervals (CIs) for cohort studies or odds ratios (ORs) and 95% confidence interval using inverse variance method. Of the nine studies included, five were cohort studies that used HR as a measurement type for their statistical analysis and four were case-control or cohort studies that used OR as a measurement type. Increased breast density over time in cohort studies was associated with higher breast cancer risk (HR: 1.61; 95% CI: 1.33-1.96) whereas decreased breast density over time was associated with lower breast cancer risk (HR: 0.78; 95% CI: 0.71-0.87). Similarly, increased breast density over time was associated with higher breast cancer risk in studies presented ORs (pooled OR: 1.85; 95% CI: 1.29-2.65). Our findings imply that an increase in breast density over time seems to be linked to an increased risk of breast cancer, whereas a decrease in breast density over time seems to be linked to a lower risk of breast cancer.

Keywords: breast cancer risk; breast density; mammography; meta-analysis.

Figure 1

Flowchart of the study selection process.

Figure 2

Pooled analysis for breast cancer risk in relation to increased breast density over time (cohort studies). Kim 2021a: A to C; Kim 2021b: A to D; Kim 2021c: B to C; Kim 2021d: B to D; Román 2019a: B to C; and Román 2019b: B to D.

Figure 3

Pooled analysis for breast cancer risk in relation to increased breast density over time (studies presenting odds ratios). Gils 1999a: <5% to >25%; Gils 1999b: 5–25% to >25%; Kerlikowske 2007a: A to C; Kerlikowske 2007b: B to C; and Kerlikowske 2007c: B to D.

Figure 4

Pooled analysis for breast cancer risk in relation to decreased breast density over time (cohort studies). Kim 2021a: C to A; Kim 2021b: C to B; Kim 2021c: D to A; Kim 2021d: D to B; Román 2019a: C to A; Román 2019b: C to B; Román 2019c: D to A; and Román 2019d: D to B.

Figure 5

Pooled analysis for breast cancer risk in relation to decreased breast density over time (studies presenting odds ratios). Gils 1999a: >25% to <5%; Gils 1999b: >25% to 5–25%; Kerlikowske 2007a: C to A; Kerlikowske 2007b: C to B; Kerlikowske 2007c: D to A; Kerlikowske 2007d: D to B; Lokate 2013a: 25–50% to <5%; Lokate 2013b: 25–50% to 5–25%; and Lokate 2013c: >50% to 5–25%.