Table 3.

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

Controls (n = 1,569)
ER- (n = 364)
ER+ (n = 533)
P*
n(%)n(%)OR(95% CI)n(%)OR(95% CI)
Among HER2-n = 252n = 356
OC use (y)
Never/<1407(25.9)32(12.7)1.0Reference92(25.9)1.0Reference
1+1,162(74.1)220(87.3)2.2(1.4-3.5)263(74.1)1.1(0.8-1.6)0.01
OC duration (y)
1 to <3327(20.8)45(17.9)1.4(0.8-2.6)81(22.8)1.3(0.9-2.0)
3 to <6357(22.8)72(28.6)2.5(1.5-4.4)87(24.5)1.2(0.8-1.8)
6+478(30.5)103(40.9)2.5(1.5-4.2)95(26.8)0.9(0.6-1.3)
P for trend0.030.05<0.001
Age at first use
22+260(16.6)45(17.9)2.0(1.1-3.6)67(18.9)1.1(0.7-1.8)
18 to <22674(43.0)122(48.4)2.0(1.2-3.3)148(41.7)1.0(0.7-1.5)
<18228(14.5)53(21.0)3.1(1.7-5.5)48(13.5)1.3(0.8-2.2)
P for trend0.170.510.80
Years since first use
1 to <15313(19.9)50(19.8)2.1(1.1-4.0)39(11.0)1.0(0.6-1.9)
15 to <20462(29.4)104(41.3)2.7(1.6-4.5)96(27.0)1.0(0.7-1.5)
20+387(24.7)66(26.2)1.7(1.0-3.0)128(36.1)1.2(0.8-1.8)
P for trend0.880.580.67
Years since last use
Current120(7.6)19(7.5)2.2(1.0-5.2)8(2.3)0.3(0.1-1.1)
1 to <5190(12.1)41(16.3)3.5(1.9-6.6)35(9.9)1.3(0.7-2.2)
5 to <10255(16.3)56(22.2)2.6(1.5-4.6)44(12.4)0.8(0.4-1.3)
10 to <15339(21.6)72(28.6)2.4(1.4-4.1)83(23.4)1.2(0.8-1.8)
15+258(16.4)32(12.7)1.1(0.6-2.1)93(26.2)1.3(0.9-2.1)
P for trend0.040.03<0.001
Among HER2+n = 112n = 177
OC use (y)
Never/<1407(25.9)27(24.1)1.0Reference46(26.0)1.0Reference
1+1,162(74.1)85(75.9)1.6(0.8-3.0)131(74.0)1.0(0.6-1.5)0.18
OC duration (y)
1 to <3327(20.8)21(18.8)1.5(0.7-3.2)37(20.9)1.0(0.5-1.7)
3 to <6357(22.8)26(23.2)1.5(0.7-3.3)35(19.8)1.0(0.6-1.8)
6+478(30.5)38(33.9)1.7(0.8-3.4)59(33.3)1.0(0.6-1.7)
P for trend0.730.910.83
Age at first use (y)
22+260(16.6)19(17.0)1.4(0.6-3.2)28(15.8)0.8(0.4-1.5)
18 to <22674(43.0)48(42.9)1.4(0.7-2.8)72(40.7)0.9(0.5-1.4)
<18228(14.5)18(16.1)2.3(1.0-5.1)31(17.5)1.5(0.8-2.8)
P for trend0.260.090.79
Years since first use
1 to <15313(19.9)20(17.9)1.3(0.5-3.4)23(13.0)0.9(0.4-1.8)
15 to <20462(29.4)33(29.5)1.6(0.8-3.2)44(24.9)0.8(0.5-1.4)
20+387(24.7)32(28.6)1.7(0.8-3.7)64(36.2)1.3(0.7-2.2)
P for trend0.420.080.62
Years since last use
Current120(7.6)5(4.5)1.2(0.3-4.6)11(6.2)1.2(0.5-2.9)
1 to <5190(12.1)22(19.6)3.5(1.5-8.1)18(10.2)1.2(0.6-2.6)
5 to <10255(16.3)15(13.4)1.3(0.6-3.1)21(11.9)0.7(0.4-1.4)
10 to <15339(21.6)19(17.0)1.3(0.6-2.8)39(22.0)0.8(0.5-1.5)
15+258(16.4)24(21.4)1.3(0.6-3.0)42(23.7)1.2(0.7-2.1)
P for trend0.240.840.36
  • 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).

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