Table 3.

Distribution of breast cancer risk factors by quintiles of percent and absolute dense volume

Percent dense volume (%)Absolute dense volume (cm3)
Q1 (<4.9)Q2 (4.9–6.5)Q3 (6.6–9.0)Q4 (9.1–13.0)Q5 (>13.0)Q1 (<39)Q2 (39–50)Q3 (51–63)Q4 (64–83)Q5 (>83)
N = 8,221N = 8,220N = 8,221N = 8,220N = 8,220P trendN = 8,221N = 8,220N = 8,221N = 8,220N = 8,220P trend
Age (years), mean59.157.955.952.749.3<0.00156.656.855.754.251.6<0.001
BMI (kg/m2), mean29.226.625.023.722.4<0.00123.225.025.826.326.4<0.001
Age at menarche (years), mean13.013.113.113.213.2<0.00113.213.213.113.113.0<0.001
Parity, %<0.001<0.001
 011.810.911.512.114.38.710.011.713.716.6
 114.213.613.914.014.912.612.413.914.916.8
 247.247.648.050.047.748.550.248.848.047.1
 ≥326.827.926.723.921.030.227.525.723.419.5
Age at first birth (years), mean25.626.126.927.828.9<0.00126.926.726.727.028.0<0.001
Menopausal status, %<0.001<0.001
 Premenopausal21.526.334.750.168.332.531.335.944.057.2
 Perimenopausal/unknown2.83.33.53.63.12.72.93.33.63.8
 Postmenopausal75.770.461.846.328.664.865.860.852.439.0
Ever OC use, %74.378.380.482.283.3<0.00178.879.479.579.881.20.003
HRT use, %a<0.0010.19
 Never70.169.168.467.769.369.169.069.469.167.9
 Former26.026.225.524.421.625.525.725.125.224.4
 Current4.04.66.18.09.10.0015.45.35.55.77.9
Benign breast disease, %17.820.622.024.026.4<0.00120.721.220.822.925.2<0.001
Family history breast cancer, %12.713.013.113.613.70.0312.312.913.413.314.20.001
  • aIn postmenopausal women only. Percent and absolute dense volumes were derived from the mediolateral oblique view.