Table 3.

The association between reproductive factors and invasive breast cancer risk by the source of data on ER and PR status among women ages 35 to 64 y in the Women's CARE Study

No. of controlsNo. of casesMultivariable adjusted* odds ratio (95% CI)
ER−/PR−ER+/PR+ER+/PR−ER−/PR+ER−/PR−ER+/PR+ER+/PR−ER−/PR+
Number of full-term pregnancies*
ER/PR measured in a centralized pathology laboratory
    Never pregnant1782659108ReferenceReferenceReferenceReference
    1315647816111.25 (0.76-2.07)0.85 (0.57-1.27)0.87 (0.38-2.01)0.77 (0.30-1.99)
    257611212019221.28 (0.80-2.04)0.69 (0.48-1.00)0.58 (0.26-1.30)0.87 (0.37-2.03)
    339657801261.00 (0.60-1.67)0.69 (0.47-1.03)0.53 (0.22-1.28)0.35 (0.12-1.05)
    ≥440558711370.99 (0.59-1.68)0.60 (0.39-0.92)0.55 (0.22-1.34)0.44 (0.15-1.31)
    Ptrend0.380.0080.090.05
    Pregnant but no full-term pregnancy1592538430.92 (0.50-1.67)0.74 (0.46-1.19)0.44 (0.13-1.44)0.38 (0.10-1.46)
ER/PR from SEER registries
    Never pregnant178196888ReferenceReferenceReferenceReference
    1315469215161.20 (0.68-2.13)0.85 (0.58-1.24)1.15 (0.47-2.81)1.07 (0.44-2.61)
    25768214930121.23 (0.72-2.10)0.75 (0.53-1.05)1.23 (0.54-2.76)0.47 (0.19-1.19)
    33965685951.29 (0.74-2.28)0.64 (0.44-0.94)0.49 (0.18-1.32)0.31 (0.10-0.99)
    ≥440547761881.04 (0.57-1.87)0.57 (0.38-0.85)0.89 (0.36-2.20)0.53 (0.18-1.54)
    Ptrend0.980.0020.200.02
    Pregnant but no full-term pregnancy1591643830.77 (0.38-1.57)0.71 (0.45-1.11)1.30 (0.47-3.61)0.38 (0.10-1.47)
ER/PR status consistently ascertained by both sources
    Never pregnant1781654ReferenceReference
    131538691.19 (0.64-2.23)0.83 (0.55-1.26)
    2576781061.40 (0.79-2.49)0.69 (0.47-1.01)
    339648691.33 (0.72-2.44)0.67 (0.45-1.02)
    ≥440544621.15 (0.61-2.17)0.59 (0.38-0.92)
    Ptrend0.750.01
    Pregnant but no full-term pregnancy15916320.94 (0.45-1.96)0.67 (0.41-1.11)
Age at first full-term pregnancy, y
ER/PR measured in a centralized laboratory
    ≤1958696872210ReferenceReferenceReferenceReference
    20-2461810113417161.06 (0.77-1.46)1.38 (1.01-1.89)0.60 (0.31-1.19)1.47 (0.64-3.38)
    25-29282538515151.19 (0.79-1.80)1.90 (1.29-2.78)1.15 (0.53-2.51) 2.80 (1.12-7.02)
    ≥302064143651.25 (0.76-2.05)1.26 (0.77-2.06)0.58 (0.20-1.72)1.14 (0.32-4.03)
    Ptrend0.310.050.630.29
ER/PR from SEER registries
    ≤1958681992411ReferenceReferenceReferenceReference
    20-246188015521121.01 (0.71-1.43)1.39 (1.03-1.87)0.71 (0.37-1.35)0.98 (0.41-2.35)
    25-2928245991681.26 (0.81-1.97)1.82 (1.27-2.61)1.28 (0.60-2.72)1.38 (0.49-3.92)
    ≥30206254911101.02 (0.57-1.82)1.14 (0.72-1.81)1.37 (0.56-3.37)1.94 (0.63-5.93)
    Ptrend0.610.110.350.20
ER/PR status consistently ascertained by both sources
    ≤195867477ReferenceReference
    20-24618731221.04 (0.72-1.51)1.47 (1.06-2.05)
    25-2928238731.22 (0.76-1.96)1.83 (1.22-2.75)
    ≥3020623341.10 (0.60-2.00)1.09 (0.64-1.85)
    Ptrend0.570.18
Duration of breastfeeding, mo
ER/PR measured in a centralized laboratory
    Never7151351523225ReferenceReferenceReferenceReference
    <12033752930.99 (0.66-1.48)1.11 (0.77-1.60)0.98 (0.45-2.13)0.37 (0.11-1.28)
    1-633655659100.79 (0.55-1.13)0.75 (0.54-1.06)0.51 (0.23-1.12)0.58 (0.26-1.28)
    7-233044462860.70 (0.47-1.03)0.79 (0.55-1.12)0.52 (0.23-1.20)0.40 (0.15-1.05)
    ≥241342018220.77 (0.45-1.32)0.55 (0.31-0.96)0.32 (0.07-1.43)0.31 (0.07-1.47)
    Ptrend0.050.020.020.03
ER/PR from SEER registries
    Never7151111733921ReferenceReferenceReference
    <12032960750.93 (0.59-1.45)1.16 (0.82-1.64)0.60 (0.26-1.38)0.76 (0.28-2.10)
    1-633640791370.70 (0.47-1.06)0.80 (0.58-1.10)0.61 (0.31-1.19)0.55 (0.22-1.37)
    7-233043470970.64 (0.41-0.98)0.78 (0.56-1.10)0.50 (0.23-1.08)0.65 (0.26-1.67)
    ≥241341720410.74 (0.41-1.34)0.55 (0.32-0.93)0.56 (0.19-1.68)0.24 (0.03-1.89)
    Ptrend0.030.010.050.10
ER/PR status consistently ascertained by both sources
    Never71596130ReferenceReference
    <120329461.08 (0.68-1.70)1.15 (0.78-1.70)
    1-633637600.79 (0.52-1.20)0.84 (0.59-1.19)
    7-2330431540.69 (0.44-1.09)0.83 (0.57-1.20)
    ≥2413415160.77 (0.41-1.42)0.58 (0.32-1.05)
    Ptrend0.090.06
  • *Adjusted for categorical variables of age, race, family history of breast cancer, age at menarche, education and study site.

  • Additionally adjusted for number of full-term-pregnancies and mutually adjusted for age at first full-term pregnancy and duration of breastfeeding.