Table 2

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 premenopausal 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)
 ≤11204(17)122(25)1.0044(17)1.000.04
 12336(28)124(25)0.59(0.39–0.89)85(32)1.08(0.62–1.88)
 13402(33)137(28)0.50(0.33–0.75)83(31)1.02(0.60–1.76)
 ≥14270(22)112(23)0.49(0.31–0.76)55(21)1.12(0.62–2.03)
Parity
 Nulliparousc207(17)82(17)1.0048(18)0.32
 1178(15)75(15)0.61(0.35–1.06)48(18)0.99(0.50–1.95)
 2530(43)224(45)0.65(0.41–1.04)122(45)1.09(0.61–1.95)
 ≥3313(26)115(23)0.44(0.26–0.75)52(19)0.90(0.46–1.76)
Age at first live birth (yrs)
 13–23382(31)141(29)1.0084(31)1.000.24
 24–27320(26)130(26)1.19(0.81–1.77)61(23)0.88(0.54–1.46)
 ≥28315(26)141(29)1.08(0.73–1.60)77(29)1.00(0.60–1.65)
 Nulliparous206(17)82(17)1.79(1.10–2.91)48(18)0.93(0.51–1.68)
Duration of OCd (yr)
 Never or <1329(29)145(33)1.0055(23)1.000.41
 ≤4247(22)91(21)0.79(0.53–1.19)50(21)1.27(0.75–2.17)
 5–9250(22)93(21)0.90(0.60–1.35)54(23)1.08(0.62–1.87)
 ≥10292(26)110(25)0.92(0.61–1.37)81(34)1.33(0.79–2.25)
BMI (kg/m2)e
 ≤25721(59)295(60)1.00155(59)1.000.03
 25.1–27165(14)68(14)1.14(0.76–1.72)38(14)1.36(0.80–2.31)
 >27335(27)126(26)0.71(0.50–1.00)72(27)1.35(0.89–2.05)
Alcohol (drinks/wk)f
 0309(26)129(27)1.0050(20)1.000.03
 ≤1319(27)122(26)1.08(0.72–1.60)75(29)1.31(0.78–2.19)
 1.5–3324(27)112(23)0.84(0.55–1.28)75(29)1.36(0.81–2.28)
 ≥3.5248(21)116(24)1.38(0.91–2.10)56(22)0.92(0.51–1.68)
Cigarette smoking (pack-years)
 0651(56)257(54)1.00124(49)1.000.75
 0.1–10241(21)93(20)0.91(0.62–1.34)64(25)1.05(0.66–1.68)
 >10278(24)124(26)1.10(0.77–1.57)66(26)1.31(0.83–2.06)
Breast feeding (mos)
 Never or nulliparous557(47)209(44)1.00140(53)1.000.12
 1–6274(23)112(23)1.17(0.77–1.78)56(21)0.70(0.41–1.19)
 >6367(31)160(33)1.41(0.96–2.08)70(26)0.86(0.53–1.39)
Benign breast disease
 No998(83)238(53)1.00154(63)1.000.44
 Yes200(17)212(47)3.73(2.73–5.09)92(37)3.15(2.10–4.72)
Family history breast cancerg
 No1102(93)400(84)1.00221(85)1.000.32
 Yes78(7)77(16)1.73(1.08–2.76)38(15)2.35(1.35–4.10)
Age group (yrs)
 25–34124(10)27(5)n/ah40(15)n/a
 35–39212(17)64(13)54(20)
 40–44324(26)129(26)75(28)
 45–49381(31)177(35)79(29)
 50–64198(16)103(21)23(9)
  • a MVOR, model is adjusted for all other variables plus age (continuous) and current strenuous activity.

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

  • f Includes beer, wine and liquor.

  • g First degree relative.

  • h n/a, not available.