Table 3

Distribution (n, %) and MVOR estimates and 95% CIs for several hormone-related and nonhormone related risk factors and breast cancer characterized by ER+PR+ and ER−PR− subgroups among postmenopausal women

Note: the control group is the same for both ERPR subgroup analyses.

Risk factorControlsER+PR+ premenopausal casesER−PR− premenopausal casesPb
n(%)n(%)MVORa(95% CI)n(%)MVORa(95% CI)
Age at menarche (yrs)
 ≤11431(18)255(19)1.00102(23)1.000.24
 12541(23)344(25)1.27(0.97–1.67)110(24)1.03(0.70–1.52)
 13651(27)392(29)1.18(0.90–1.54)109(24)0.96(0.65–1.42)
 ≥14778(32)376(28)0.84(0.64–1.10)133(29)0.94(0.64–1.37)
Parity
 Nulliparousc275(11)195(14)1.0063(13)1.000.84
 1251(10)168(12)0.95(0.66–1.36)56(12)0.93(0.55–1.55)
 2716(29)436(31)0.84(0.61–1.15)137(30)0.73(0.46–1.15)
 ≥31196(49)594(43)0.71(0.53–0.97)206(45)0.72(0.46–1.12)
Age at first live birth (yr)
 13–231216(50)590(43)1.00207(45)1.000.50
 24–27560(23)323(23)1.21(0.97–1.52)113(25)1.31(0.95–1.81)
 ≥28367(15)275(20)1.64(1.28–2.10)77(17)1.30(0.89–1.89)
 Nulliparous273(11)195(14)1.46(1.08–1.97)63(12)1.46(0.95–2.26)
Duration of OCd (yr)
 Never or <11373(62)834(64)1.00225(52)1.000.27
 ≤4313(14)174(13)0.85(0.65–1.11)72(17)1.04(0.71–1.53)
 5–9283(13)153(12)0.86(0.64–1.15)60(14)1.06(0.70–1.59)
 ≥10259(12)149(11)0.95(0.71–1.27)72(17)1.41(0.96–2.08)
Age at menopause (yr)
 <45812(35)389(29)1.00141(32)1.000.32
 45–49622(27)351(26)1.17(0.92–1.49)122(28)1.52(1.08–2.16)
 ≥50890(38)601(45)1.50(1.19–1.88)174(40)1.63(1.15–2.30)
Duration of HRTe use (yr)
 Never or <11498(66)920(69)1.00297(68)1.000.40
 ≤2280(12)130(10)0.77(0.57–1.03)56(13)0.89(0.60–1.32)
 2–11243(11)144(11)0.97(0.72–1.30)42(10)0.80(0.52–1.24)
 ≥12247(11)131(10)0.94(0.67–1.31)42(10)1.26(0.79–2.01)
BMI (kg/m2)f
 20–251008(42)489(36)1.00172(38)1.000.29
 <20119(5)45(3)0.72(0.43–1.21)25(5)1.34(0.72–2.49)
 25.1–27392(16)208(15)1.10(0.84–1.43)72(16)1.09(0.74–1.61)
 >27881(37)631(46)1.61(1.32–1.98)190(41)1.48(1.09–1.99)
Alcohol (drinks/week)g
 0766(33)435(33)1.00144(33)1.000.89
 ≤1591(26)330(25)1.03(0.23–1.30)112(25)1.06(0.75–1.50)
 1.5–3483(21)256(19)0.90(0.69–1.15)93(21)0.90(0.62–1.32)
 ≥3.5471(20)311(23)1.27(1.00–1.64)93(21)1.13(0.79–1.64)
Cigarette smoking (pack-years)
 01287(56)693(52)1.00210(48)1.000.07
 0.1–10310(13)174(13)1.04(0.79–1.37)56(13)0.89(0.58–1.37)
 >10714(31)459(35)1.16(0.94–1.42)175(40)1.53(1.15–2.04)
Breast feeding (mos)
 Never or nulliparous1178(50)705(52)1.00237(52)1.000.64
 1–6606(26)332(24)0.99(0.78–1.25)114(25)1.00(0.72–1.40)
 >6595(25)332(24)0.92(0.73–1.16)107(23)1.09(0.77–1.52)
Benign breast disease
 No1784(77)598(48)1.00215(52)1.000.06
 Yes524(23)660(53)3.83(3.17–4.61)199(48)2.95(2.25–3.86)
Family history breast cancerh
 No1990(87)1089(81)1.00374(85)1.000.64
 Yes291(13)255(19)1.30(1.01–1.66)68(15)1.19(0.83–1.71)
Age group (yr)
 25–49222(9)140(10)77(17)
 50–54360(15)167(12)78(17)
 55–59459(19)270(19)90(19)
 60–64458(19)270(19)83(18)
 65–69522(21)305(22)80(17)
 70–74431(18)249(18)58(12)
  • a MVOR, model is adjusted for all other variables plus continuous age and oophorectomy.

  • b P (likelihood ratio test) for heterogeneity in MVORs between ER−PR− and ER+PR+; calculated using polytomous logistic regression.

  • c Includes both never pregnant and no live births.

  • d OC, oral contraceptives.

  • e HRT, includes both estrogen and estrogen/progestin regimens.

  • f BMI was calculated using “weight 2 years ago” (prediagnosis).

  • g Includes beer, wine, and liquor.

  • h First degree relative.