Table 4.

Multivariate adjusted case-control odds ratios and 95% CIs for all breast cancer cases, triple-negative and non-triple-negative cases, in relation to oral contraceptive risk factors, stratified by age at diagnosis ≤40 and 41-45 y, 1983-1992

Triple-negative status
P*
Controls (n = 1,569)

All breast cancer (n = 897)
Triple-negative (n = 187)
Non-triple-negative (n = 710)
n(%)n(%)OR(95% CI)n(%)OR(95% CI)n(%)OR(95% CI)
Among women40 y of age
n = 1,156n = 590n = 141n = 449
OC use (y)
Never/<1299(25.9)121(20.5)1.0Reference11(7.8)1.0Reference110(24.5)1.0Reference
1+857(74.1)469(79.5)1.6(1.1-2.1)130(92.2)4.2(1.9-9.3)339(75.5)1.2(0.9-1.7)<0.001
OC duration (y)
1 to <3242(20.9)126(21.4)1.5(1.0-2.2)31(22.0)3.0(1.2-7.3)95(21.2)1.3(0.9-2.0)
3 to <6261(22.6)141(23.9)1.6(1.1-2.4)39(27.7)4.9(2.1-11.6)102(22.7)1.2(0.8-1.9)
6+354(30.6)202(34.2)1.5(1.1-2.2)60(42.6)4.7(2.0-10.8)142(31.6)1.2(0.8-1.7)
P for trend0.860.170.580.10
Age at first use (y)
22+166(14.4)79(13.4)1.3(0.8-2.1)20(14.2)3.5(1.4-9.1)59(13.1)1.1(0.7-1.8)
18 to <22499(43.2)270(45.8)1.4(1.0-2.0)75(53.2)3.7(1.7-8.5)195(43.4)1.1(0.8-1.6)
<18192(16.6)120(20.3)2.3(1.5-3.5)35(24.8)6.4(2.6-15.6)85(18.9)1.8(1.2-2.8)
P for trend0.020.120.040.93
Years since first use
<20721(62.4)368(62.4)1.5(1.1-2.1)108(76.6)4.2(1.9-9.5)260(57.9)1.2(0.8-1.7)
20+136(11.8)101(17.1)1.8(1.2-2.9)22(15.6)4.2(1.6-10.8)79(17.6)1.6(1.0-2.5)0.45
Years since last use
Current117(10.1)43(7.3)1.2(0.6-2.1)16(11.3)4.5(1.6-13.1)27(6.0)0.8(0.4-1.5)
1 to <10388(33.6)210(35.6)1.7(1.2-2.4)62(44.0)5.1(2.2-11.6)148(33.0)1.3(0.9-1.9)
10 to <15240(20.8)148(25.1)1.7(1.1-2.4)41(29.1)4.2(1.7-9.9)107(23.8)1.4(0.9-2.1)
15+112(9.7)68(11.5)1.3(0.8-2.1)11(7.8)2.1(0.7-6.2)57(12.7)1.2(0.7-2.0)
P for trend0.950.150.460.07
Among women 41-45 y of age
n = 413n = 307n = 46n = 261
OC use (y)
Never/<1108(26.2)76(24.8)1.0Reference11(23.9)1.0Reference65(25.0)1.0Reference
1+305(73.8)230(75.2)1.0(0.7-1.5)35(76.1)0.9(0.4-2.2)195(75.0)1.0(0.7-1.6)0.93
OC duration (y)
1 to <385(20.6)58(19.0)0.9(0.5-1.6)4(8.7)0.4(0.1-1.6)54(20.8)1.0(0.6-1.8)
3 to <696(23.2)79(25.8)1.2(0.7-2.0)12(26.1)1.1(0.4-3.0)67(25.8)1.2(0.7-2.1)
6+124(30.0)93(30.4)0.9(0.6-1.6)19(41.3)1.3(0.5-3.3)74(28.5)0.9(0.5-1.5)
P for trend0.910.110.650.06
Age at first use (y)
22+94(22.8)80(26.1)1.0(0.6-1.8)11(23.9)0.8(0.3-2.5)69(26.5)1.1(0.6-1.9)
18 to <22175(42.4)120(39.2)1.0(0.6-1.6)17(37.0)0.9(0.4-2.3)103(39.6)1.0(0.6-1.6)
<1836(8.7)30(9.8)1.1(0.6-2.3)7(15.2)1.3(0.4-4.9)23(8.8)1.1(0.5-2.3)
P for trend0.850.571.00.59
Years since first use
<2054(13.1)41(13.4)1.0(0.5-1.9)6(13.0)1.0(0.3-3.6)35(13.5)1.0(0.5-1.9)
20+251(60.8)189(61.8)1.0(0.7-1.6)29(63.0)0.9(0.4-2.2)160(61.5)1.0(0.7-1.6)0.77
Years since last use
Current3(0.7)0(0.0)0.0N/A0(0.0)0.0N/A0(0.0)0.0N/A
1 to <1057(13.8)42(13.7)1.0(0.5-1.9)10(21.7)1.8(0.6-5.4)32(12.3)0.8(0.4-1.6)
10 to <1599(24.0)65(21.2)0.8(0.5-1.5)14(30.4)1.0(0.4-2.8)51(19.6)0.8(0.5-1.5)
15+146(35.4)123(40.2)1.1(0.7-1.8)11(23.9)0.7(0.2-1.8)112(43.1)1.2(0.8-2.0)
P for trend0.330.080.100.01
  • NOTE: Risk factors adjusted for age, family history of breast cancer, and breastfeeding history.

  • * Pheterogeneity (association of risk factor with triple-negative versus non-triple-negative breast cancer).

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