Table 3.

HRs of second breast cancers according to breast laterality by four measures of mammographic density

Density measureFull cohortAny ipsilateral breast cancerAny contralateral breast cancer
UnadjustedAdjusted*UnadjustedAdjusted*
NNHR (95% CI)HR* (95% CI)PNHR (95% CI)HR* (95% CI)P
Parenchymal pattern
    N197101.01.00.2241.01.00.06
    P1209381.8 (0.9-3.7)1.8 (0.9-3.7)121.5 (0.5-4.5)1.7 (0.5-5.2)
    P26081112.0 (1.0-3.7)1.7 (0.8-3.3)431.9 (0.7-5.3)2.8 (1.0-8.3)
    DY2153.3 (1.1-9.7)2.7 (0.9-8.2)00.00.0
Area of density
    Quintile 1185231.01.00.1691.01.0<0.01
    Quintile 2193361.6 (1.0-2.8)1.5 (0.9-2.6)131.5 (0.6-3.5)1.8 (0.8-4.4)
    Quintile 3190351.6 (1.0-2.8)1.5 (0.8-2.6)80.9 (0.4-2.4)1.2 (0.5-3.2)
    Quintile 4184321.5 (0.9-2.6)1.2 (0.7-2.2)111.3 (0.5-3.1)1.7 (0.7-4.3)
    Quintile 5183381.9 (1.2-3.2)1.7 (1.0-2.9)182.4 (1.1-5.3)3.0 (1.3-6.9)
Percent density
    06671.01.00.8831.01.00.04
    1-24298501.6 (0.8-3.6)1.6 (0.7-3.6)171.3 (0.4-4.5)1.6 (0.4-5.4)
    25-49314571.9 (0.9-4.1)1.7 (0.7-3.8)201.6 (0.5-5.2)2.3 (0.7-8.2)
    50-74225442.1 (0.9-4.6)1.6 (0.7-3.8)182.0 (0.6-6.8)3.6 (1.0-13.1)
    ≥753261.8 (0.6-5.5)1.2 (0.4-4.1)10.7 (0.1-6.6)1.4 (0.1-14.6)
BI-RADS density
    Almost all fat165221.01.00.3251.01.00.02
    Scattered fibroglandular292471.3 (0.8-2.1)1.2 (0.7-2.1)232.8 (1.0-7.2)3.8 (1.4-10.2)
    Heterogeneously dense328661.6 (1.0-2.6)1.4 (0.8-2.4)232.4 (0.9-6.4)3.9 (1.4-10.8)
    Extremely dense125271.8 (1.0-3.1)1.3 (0.7-2.6)82.3 (0.7-7.0)5.0 (1.4-17.9)
  • *Adjusted for age (continuous), BMI (<20, 20 to <25, 25 to <30, 30 to <35, ≥35), radiotherapy (yes, no), tamoxifen (yes, no), and diagnosis year (1990-1991, 1992-1993, 1994-1995, 1996-1997).

  • P-value for linear trend.