Table 2.

Multivariate RR (95% CI) of breast cancer by quartile of plasma prolactin concentrations among predominately premenopausal women

Prolactin concentrationsPtrend *
Quartile 1Quartile 2Quartile 3Quartile 4
All cases and controls
    All cases (n = 312 cases) 1.0 (Reference)1.1 (0.8-1.7)0.9 (0.6-1.4)1.5 (1.0-2.3)0.03
    Invasive only (n = 216 cases) §1.0 (Reference)1.1 (0.7-1.7)0.9 (0.5-1.4)1.5 (0.9-2.4)0.04
    ER+/PR+ (n = 142 cases) §1.0 (Reference)1.4 (0.8-2.5)1.2 (0.7-2.2)1.9 (1.1-3.3)0.04
All premenopausal cases and controls
    All cases (n = 235 cases) 1.0 (Reference)1.2 (0.7-1.9)0.9 (0.6-1.5)1.5 (1.0-2.5)0.06
    Invasive only (n = 159 cases) §1.0 (Reference)1.2 (0.7-2.0)0.9 (0.5-1.6)1.6 (0.9-2.7)0.09
    ER+/PR+ (n = 109 cases) §1.0 (Reference)1.5 (0.8-3.0)1.2 (0.6-2.5)1.9 (1.0-3.7)0.10
Follicular phase prolactin
    All cases (n = 193 cases) 1.0 (Reference)1.0 (0.6-1.6)0.7 (0.4-1.3)1.3 (0.8-2.1)0.28
    Invasive only (n = 130 cases) §1.0 (Reference)1.1 (0.6-1.9)0.7 (0.4-1.4)1.3 (0.7-2.3)0.41
    ER+/PR+ (n = 89 cases) §1.0 (Reference)1.2 (0.6-2.3)1.0 (0.5-2.0)1.5 (0.7-3.1)0.25
Luteal phase prolactin
    All cases (n = 197 cases) 1.0 (Reference)0.9 (0.5-1.5)1.0 (0.6-1.6)1.0 (0.6-1.7)0.79
    Invasive only (n = 131 cases) §1.0 (Reference)0.6 (0.3-1.2)0.8 (0.5-1.5)0.9 (0.5-1.7)0.85
    ER+/PR+ (n = 89 cases) §1.0 (Reference)0.7 (0.3-1.4)0.9 (0.4-1.7)0.8 (0.4-1.6)0.71
Average follicular and luteal
    All cases (n = 193 cases) 1.0 (Reference)1.2 (0.7-2.0)0.7 (0.4-1.2)1.3 (0.8-2.3)0.40
    Invasive only (n = 130 cases) §1.0 (Reference)1.1 (0.6-1.9)0.6 (0.3-1.2)1.3 (0.7-2.4)0.40
    ER+/PR+ (n = 89 cases) §1.0 (Reference)1.0 (0.7-2.8)0.9 (0.4-1.8)1.4 (0.7-2.9)0.49
  • * Determined using batch-specific quartile medians.

  • For those with timed samples, we used the average of the two phases; for women with untimed samples, we used their individual sample.

  • Conditional logistic regression adjusting for BMI at age 18, weight change from age 18 to blood draw, family history of breast cancer, and age at menarche.

  • § Unconditional logistic regression adjusting for BMI at age 18, weight change from age 18 to blood draw, family history of breast cancer, age at menarche, and matching factors.