Table 4.

Duration of oral contraceptive use, current use, and risk of ER+, ER, triple-negative (ER/PR/HER2), and HER2-overexpressing (ER/HER2+) breast cancera

ControlsER+ERER/PR/HER2ER/HER2+
n (%)n (%)ORb95% CIn (%)ORb95% CIn (%)ORb95% CIn (%)ORb95% CI
All (age 20–44)n = 882n = 730n = 246n = 171n = 56
Lifetime duration of use
 Never103 (11.7)92 (12.6)1.0(ref)26 (10.6)1.0(ref)15 (8.8)1.0(ref)11 (19.6)1.0(ref)
 Ever779 (88.3)638 (87.4)1.0(0.7–1.3)220 (89.4)1.1(0.7–1.8)156 (91.2)1.4(0.8–2.5)45 (80.4)0.5(0.3–1.1)
  <15 years677 (76.9)499 (68.5)0.9(0.6–1.2)183 (75.0)1.0(0.7–1.7)131 (77.5)1.3(0.7–2.4)38 (67.9)0.5(0.2–1.1)
  ≥15 years100 (11.4)137 (18.8)1.6(1.0–2.3)c35 (14.3)1.5(0.8–2.7)23 (13.6)1.7(0.8–3.6)7 (12.5)0.7(0.2–1.9)
Current use and duration of use in the prior 5 years
 Current use144 (16.3)150 (20.5)1.2(0.9–1.8)49 (19.9)1.3(0.7–2.2)34 (19.9)1.6(0.8–3.2)11 (19.6)0.7(0.3–1.6)
  <5 years89 (10.1)80 (11.0)1.1(0.7–1.6)22 (8.9)0.9(0.5–1.7)18 (10.5)1.3(0.6–2.8)4 (7.1)
  ≥5 years54 (6.1)70 (9.6)1.5(1.0–2.4)27 (11.0)2.0(1.1–3.9)c16 (9.4)2.2(1.0–4.7)7 (12.5)1.2(0.4–3.4)
Age 20–39n = 355n = 249n = 122n = 82n = 30
Lifetime duration of use
 Never44 (12.4)33 (13.3)1.0(ref)12 (9.8)1.0(ref)7 (8.5)1.0(ref)5 (16.7)1.0(ref)
 Ever311 (87.6)216 (86.7)1.0(0.6–1.6)110 (90.2)1.3(0.6–2.6)75 (91.5)1.7(0.7–4.0)25 (83.3)0.6(0.2–1.7)
  <15 years284 (80.0)179 (72.5)0.9(0.5–1.5)93 (76.9)1.2(0.6–2.4)66 (81.5)1.6(0.7–3.9)20 (66.7)0.5(0.2–1.6)
  ≥15 years27 (7.6)35 (14.2)1.8(0.9–3.7)16 (13.2)2.2(0.9–5.6)8 (9.9)2.1(0.7–7.0)5 (16.7)1.4(0.3–5.8)
Current use and duration of use in the prior 5 years
 Current use72 (20.3)67 (26.9)1.3(0.7–2.3)30 (24.6)1.5(0.7–3.4)19 (23.2)1.8(0.7–4.9)8 (26.7)0.8(0.3–2.9)
  <5 years55 (15.5)40 (16.1)1.0(0.5–1.9)14 (11.5)0.9(0.4–2.3)10 (12.2)1.3(0.4–3.7)4 (13.3)
  ≥5 years17 (4.8)27 (10.8)2.2(1.0–4.7)16 (13.1)3.5(1.3–9.0)c9 (11.0)3.7(1.2–11.8)c4 (13.3)
Age 40–44n = 527n = 481n = 124n = 89n = 26
Lifetime duration of use
 Never59 (11.2)59 (12.3)1.0(ref)14 (11.3)1.0(ref)8 (9.0)1.0(ref)6 (23.1)1.0(ref)
 Ever468 (88.8)422 (87.7)0.9(0.6–1.4)110 (88.7)0.9(0.5–1.7)81 (91.0)1.2(0.5–2.7)20 (76.9)0.4(0.1–1.0)
  <15 years393 (74.9)320 (66.5)0.8(0.6–1.3)90 (73.2)0.9(0.5–1.7)65 (73.9)1.2(0.5–2.6)18 (69.2)0.4(0.1–1.1)
  ≥15 years73 (13.9)102 (21.2)1.4(0.9–2.4)19 (15.4)1.0(0.5–2.3)15 (17.0)1.5(0.6–3.8)2 (7.7)
Current use and duration of use in the prior 5 years
 Current use72 (13.7)83 (17.3)1.2(0.7–1.9)19 (15.3)1.0(0.5–2.2)15 (16.9)1.4(0.6–3.7)3 (11.5)
  <5 years34 (6.5)40 (8.3)1.1(0.6–2.0)8 (6.5)0.9(0.3–2.3)8 (9.0)1.5(0.5–4.6)0 (0.0)
  ≥5 years37 (7.0)43 (8.9)1.3(0.7–2.2)11 (8.9)1.2(0.5–3.0)7 (7.9)1.4(0.5–4.2)3 (11.5)

Abbreviations: OC, oral contraceptive; OR, odds ratio; CI, confidence interval; ER, estrogen receptor.

  • aEver use is defined as OC use for ≥6 months and current use is defined as use of OCs within the prior year. ORs resulting from cells with <5 women are not displayed.

  • bORs are adjusted for age, year, and race/ethnicity.

  • cP < 0.05.