Table 2.

Multivariate adjusted case-control odds ratios and 95% CIs for all breast cancer cases defined by HER2 and ER status in relation to oral contraceptive use among women 45 y of age and younger, 1983-1992

ER status
P*HER2 status
P

Controls (n = 1,569)
ER- (n = 364)
ER+ (n = 533)
HER2- (n = 608)
HER2+ (n = 289)
n(%)n(%)OR(95% CI)n(%)OR(95% CI)n(%)OR(95% CI)n(%)OR(95% CI)
OC use (y)
    Never/<1407(25.9)59(16.2)1.0Reference138(25.9)1.0Reference124(20.4)1.0Reference73(25.3)1.0Reference
    1+1,162(74.1)305(83.8)2.0(1.3-2.9)394(74.1)1.1(0.8-1.4)0.005483(79.6)1.4(1.1-1.9)216(74.7)1.2(0.8-1.7)0.27
OC duration (y)
    1 to <3327(20.8)66(18.1)1.5(0.9-2.4)118(22.2)1.2(0.8-1.7)126(20.8)1.4(0.9-2.0)58(20.1)1.1(0.7-1.8)
    3 to <6357(22.8)98(26.9)2.2(1.4-3.4)122(22.9)1.1(0.8-1.6)159(26.2)1.6(1.1-2.3)61(21.1)1.2(0.7-1.9)
    6+478(30.5)141(38.7)2.2(1.4-3.4)154(28.9)0.9(0.6-1.3)198(32.6)1.4(1.0-2.0)97(33.6)1.2(0.8-1.8)
    P for trend0.050.150.0040.940.790.89
Age at first use (y)
    22+260(16.6)64(17.6)1.7(1.1-2.9)95(17.9)1.0(0.7-1.5)112(18.5)1.4(0.9-2.0)47(16.3)1.0(0.6-1.6)
    18 to <22674(43.0)170(46.7)1.8(1.2-2.8)220(41.4)1.0(0.7-1.3)270(44.5)1.3(1.0-1.8)120(41.5)1.1(0.7-1.6)
    <18228(14.5)71(19.5)2.8(1.7-4.6)79(14.8)1.4(0.9-2.2)101(16.6)1.9(1.3-2.9)49(17.0)1.8(1.1-2.9)
    P for trend0.100.140.960.180.050.40
Years since first use
    1 to <15313(19.9)70(19.2)1.8(1.1-3.2)62(11.7)1.0(0.6-1.6)89(14.7)1.4(0.9-2.2)43(14.9)1.0(0.6-1.8)
    15 to <20462(29.4)137(37.6)2.3(1.5-3.6)140(26.3)0.9(0.6-1.3)200(32.9)1.5(1.1-2.2)77(26.6)1.0(0.6-1.6)
    20+387(24.7)98(26.9)1.7(1.1-2.8)192(36.1)1.2(0.9-1.7)194(32.0)1.4(0.9-2.0)96(33.2)1.4(0.9-2.2)
    P for trend0.800.170.400.780.070.12
Years since last use
    Current120(7.6)24(6.6)1.9(0.9-3.9)19(3.6)0.6(0.3-1.4)27(4.4)0.9(0.5-1.8)16(5.5)1.2(0.5-2.6)
    1 to <5190(12.1)63(17.3)3.6(2.1-6.0)53(10.0)1.3(0.8-2.0)76(12.5)2.0(1.3-3.1)40(13.8)1.9(1.1-3.3)
    5 to <10255(16.3)71(19.5)2.2(1.3-3.6)65(12.2)0.7(0.5-1.2)100(16.5)1.3(0.9-2.0)36(12.5)0.9(0.5-1.5)
    10 to <15339(21.6)91(25.0)2.0(1.3-3.2)122(22.9)1.0(0.7-1.5)155(25.5)1.6(1.1-2.2)58(20.1)1.0(0.6-1.5)
    15+258(16.4)56(15.4)1.2(0.7-2.0)135(25.4)1.3(0.9-1.9)125(20.6)1.3(0.9-1.9)66(22.8)1.2(0.8-2.0)
    P for trend0.020.07<0.0010.950.620.65
  • NOTE: Risk factors adjusted for age, family history of breast cancer, and breastfeeding history.

  • * Pheterogeneity (association of risk factor with ER- versus ER+ breast cancer).

  • Pheterogeneity (association of risk factor with HER2- versus HER2+ breast cancer).

  • Ptrend and Pheterogeneity among oral contraceptive users >1 y only.