Table 3

Associations between various factors and breast cancer characterized by HER-2/neu amplification status

HER-2/neu+ cases/Controls n = 115/790 OR (95% CI)aHER-2/neu− cases/Controls n = 462/790 OR (95% CI)aHER-2/neu+ cases/HER-2/neu− cases n = 115/462 OR (95% CI)b
Age at menarche
<12 years1.4 (0.8–2.2)1.3 (1.0–1.8)1.1 (0.7–1.9)
≥12 years1.01.01.0
Nulliparity/Age at first full-term pregnancy
Nulliparous1.1 (0.6–2.0)0.9 (0.6–1.4)1.2 (0.7–2.3)
>25 years0.9 (0.5–1.6)1.0 (0.7–1.4)0.9 (0.5–1.7)
≤25 years1.01.01.0
Abortion or miscarriage
Ever0.9 (0.6–1.4)0.9 (0.7–1.2)1.0 (0.6–1.6)
Never1.01.01.0
Breastfeeding
≥12 months0.3 (0.1–0.7)0.8 (0.5–1.2)0.3 (0.1–0.9)
<12 months0.7 (0.4–1.1)0.6 (0.4–0.9)1.1 (0.6–2.0)
Never1.01.01.0
Oral contraceptive use
Ever0.9 (0.5–1.5)1.2 (0.9–1.7)0.7 (0.4–1.2)
Never1.01.01.0
Hormone replacement therapyc
Ever (≥3 months)0.6 (0.3–1.0)0.8 (0.6–1.1)0.6 (0.3–1.2)
Never1.01.01.0
Body mass index
>27.3 kg/m20.6 (0.4–1.0)1.0 (0.7–1.3)0.8 (0.5–1.2)
≤27.3 kg/m21.01.01.0
Waist:hip ratio
>0.81.4 (0.9–2.3)1.4 (1.0–1.8)1.0 (0.7–1.7)
≤0.81.01.01.0
First-degree family history of breast or ovarian cancer
Yes1.7 (1.0–3.0)1.4 (1.0–2.0)1.2 (0.7–2.1)
No1.01.01.0
Medical radiation to the chest
Ever1.2 (0.5–2.8)1.1 (0.7–1.8)1.0 (0.4–2.5)
Never1.01.01.0
Alcohol drinking during most recent age range
Yes1.0 (0.6–1.5)0.9 (0.7–1.2)1.1 (0.7–1.8)
No1.01.01.0
Smoking
Ever (≥5 packs)1.1 (0.7–1.7)1.0 (0.8–1.3)1.1 (0.7–1.8)
Never1.01.01.0
Education
≥College graduate1.1 (0.5–2.3)1.0 (0.7–1.6)1.2 (0.6–2.6)
≥High school graduate to College graduate1.1 (0.6–2.0)1.1 (0.7–1.5)1.2 (0.6–2.2)
<High school graduate1.01.01.0
  • a Adjusted for all the 13 exposure variables simultaneously, as well as race, age at diagnosis/selection (5-year age group), and the offset term.

  • b Case-case ORs adjusted for all the 13 exposure variables simultaneously, as well as race and age at diagnosis/selection (two levels to reflect the sampling design for cases).

  • c Additionally adjusted for menopausal status.