Table 3.

Multivariate RR (95% CI) of breast cancer by quartile of plasma prolactin concentrations by time between blood draw and diagnosis

Prolactin concentrationsPtrend *Pheterogeneity
Quartile 1Quartile 2Quartile 3Quartile 4
All cases and controls
    <2 y (n = 122 cases)1.0 (Reference)1.0 (0.6-1.8)0.7 (0.4-1.4)1.4 (0.8-2.5)0.130.18
    2 to <3.875 y (n = 110 cases)1.0 (Reference)0.9 (0.5-1.8)1.0 (0.5-2.0)1.9 (1.0-3.4)0.01
    ≥3.875 y (n = 78 cases)1.0 (Reference)1.2 (0.6-2.5)0.9 (0.4-1.8)1.0 (0.4-2.1)0.51
All premenopausal cases and controls
    <2 y (n = 86 cases)1.0 (Reference)1.1 (0.6-2.1)0.7 (0.3-1.5)1.6 (0.8-3.0)0.110.13
    2 to <3.875 y (n = 79 cases)1.0 (Reference)0.9 (0.4-2.1)1.0 (0.5-2.1)1.8 (0.9-3.5)0.03
    ≥3.875 y (n = 70 cases)1.0 (Reference)1.5 (0.7-3.1)1.3 (0.6-2.7)1.1 (0.5-2.3)0.63
Follicular phase prolactin
    <2 y (n = 63 cases)1.0 (Reference)0.7 (0.3-1.6)0.6 (0.2-1.4)1.5 (0.7-3.3)0.080.20
    2 to <3.875 y (n = 64 cases)1.0 (Reference)1.0 (0.4-2.2)1.0 (0.5-2.4)1.5 (0.7-3.4)0.25
    ≥3.875 y (n = 66 cases)1.0 (Reference)1.1 (0.5-2.3)0.6 (0.3-1.5)0.8 (0.3-1.9)0.46
Luteal phase prolactin
    <2 y (n = 63 cases)1.0 (Reference)0.8 (0.3-2.0)1.3 (0.6-3.0)1.7 (0.8-3.7)0.270.38
    2 to <3.875 y (n = 66 cases)1.0 (Reference)0.7 (0.3-1.7)0.9 (0.4-2.0)1.1 (0.5-2.4)0.74
    ≥3.875 y (n = 68 cases)1.0 (Reference)0.9 (0.4-1.8)0.8 (0.4-1.6)0.6 (0.2-1.2)0.33
Average follicular and luteal
    <2 y (n = 63 cases)1.0 (Reference)1.0 (0.5-2.4)0.7 (0.3-1.8)2.1 (0.9-4.7)0.080.10
    2 to <3.875 y (n = 64 cases)1.0 (Reference)1.1 (0.5-2.4)0.6 (0.3-1.5)1.4 (0.6-3.1)0.49
    ≥3.875 y (n = 66 cases)1.0 (Reference)1.3 (0.6-2.6)0.7 (0.3-1.6)0.7 (0.3-1.7)0.44
  • NOTE: Adjusted for BMI at age 18, weight change from age 18 to blood draw, family history of breast cancer, age at menarche, and matching factors.

  • * Determined using batch-specific quartile medians.

  • Determined using polytomous logistic regression and the likelihood ratio test, comparing a model constraining RRs to be the same across all case groups versus a model allowing the RRs to differ across case groups.

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