Table 4

Multivariate-adjusteda ORs and 95% CIs for HER2/neu-positive (+) and HER2/neu-negative (−) breast cancer in relation to patterns of OC use by estrogen receptor status

Controls (n = 462)HER2/neu + (n = 62)HER2/neu − (n = 109)HER2/neu + OR (95% CI)HER2/neu − OR (95% CI)Ratio of the ORs (95% CI)
Among cases with ER+ tumors
OC use
 Never16821401.01.0
 Ever29441690.99 (0.55–1.80)0.93 (0.58–1.47)1.07 (0.54–2.12)
OC duration (years)b
 <53722410.88 (0.44–1.74)0.89 (0.53–1.50)0.99 (0.45–2.16)
 5–98111180.97 (0.42–2.25)0.90 (0.47–1.73)1.08 (0.41–2.82)
 ≥101768101.56 (0.59–4.13)1.17 (0.52–2.67)1.33 (0.43–4.13)
Age at first use of OC (in years)b
 <1840671.32 (0.44–3.99)1.12 (0.44–2.84)1.18 (0.32–4.35)
 18–2115218390.79 (0.39–1.62)0.95 (0.56–1.62)0.83 (0.37–1.86)
 ≥2210217231.20 (0.58–2.51)0.84 (0.46–1.53)1.44 (0.61–3.39)
Number of years since first useb
 <158610130.91 (0.36–2.34)0.78 (0.36–1.69)1.17 (0.39–3.57)
 15–1911315200.77 (0.35–1.67)0.67 (0.36–1.26)1.14 (0.46–2.84)
 ≥209516361.39 (0.62–3.11)1.36 (0.74–2.47)1.03 (0.42–2.50)
Number of years since last useb
 <57913151.71 (0.74–3.95)1.09 (0.52–2.26)1.57 (0.58–4.28)
 5–941490.84 (0.26–2.74)0.95 (0.40–2.23)0.89 (0.24–3.34)
 ≥1017442450.79 (0.39–1.57)0.87 (0.51–1.46)0.91 (0.42–1.99)
Among cases with ER− tumors
OC use
 Never16813221.01.0
 Ever29451342.58 (1.31–5.10)0.92 (0.49–1.71) 2.81 (1.18–6.67)
OC duration (years)b
 <53732202.89 (1.40–5.97)0.95 (0.47–1.92) 3.04 (1.18–7.82)
 5–9811291.90 (0.78–4.58)0.82 (0.34–1.99)2.31 (0.72–7.46)
 ≥1076752.92 (1.03–8.29)1.02 (0.31–3.29)2.87 (0.66–12.45)
Age at first use of OC (in years)b
 <18401133.72 (1.44–9.63)0.69 (0.19–2.53) 5.37 (1.20–24.01)
 18–2115220232.01 (0.93–4.34)1.29 (0.65–2.55)1.55 (0.59–4.08)
 ≥221022082.95 (1.34–6.49)0.50 (0.19–1.32) 5.92 (1.81–19.36)
Number of years since first useb
 <158617122.96 (1.27–6.92)1.21 (0.51–2.87)2.44 (0.80–7.46)
 15–1911318102.15 (0.95–4.85)0.64 (0.26–1.55) 3.38 (1.08–10.56)
 ≥209516122.76 (1.12–6.77)0.98 (0.41–2.35)2.81 (0.87–9.11)
Number of years since last useb
 <57913102.76 (1.13–6.73)1.35 (0.54–3.38)2.05 (0.62–6.77)
 5–9411093.36 (1.31–8.63)1.52 (0.58–3.98)2.21 (0.64–7.61)
 ≥101742852.29 (1.07–4.89)0.64 (0.30–1.37) 3.58 (1.30–9.83)
  • a Adjusted for age, body mass index, age at first birth, parity status, age at menarche, first-degree family history of breast cancer, prior breast biopsy, and caloric intake.

  • b Relative to never user.