Table 4.

Relationship between proximate prolactin levels and risk of breast cancer among postmenopausal cases and controls (NHS and NHSII), by breast tumor characteristics

Prolactin concentrations (ng/mL)
≤8.1>8.1–11.0>11.0–15.7>15.7P-trenda
Morphologyb
 In situ, n69465748
RR (95% CI)c1.000.75 (0.50–1.11)1.14 (0.77–1.67)1.16 (0.77–1.74)0.23
Invasive, n330293344246
RR (95% CI)c1.001.05 (0.86–1.28)1.53 (1.25–1.87)1.38 (1.11–1.73)0.0005
Histologyb
Ductal, n273233277202
RR (95% CI)c1.001.00 (0.81–1.24)1.49 (1.21–1.85)1.41 (1.12–1.78)0.0004
Lobular, n35424432
RR (95% CI)c1.001.36 (0.85–2.18)1.68 (1.04–2.71)1.51 (0.90–2.55)0.13
ER/PR Statusb
ER+/PR+, n182163205156
RR (95% CI)c1.001.03 (0.81–1.32)1.62 (1.27–2.06)1.53 (1.17–1.98)0.0002
ER+/PR, n38533934
RR (95% CI)c1.001.62 (1.04–2.50)1.46 (0.91–2.35)1.61 (0.98–2.65)0.13
ER/PR, n54364224
RR (95% CI)c1.000.78 (0.50–1.21)1.21 (0.77–1.88)0.88 (0.52–1.47)0.94
Her2 Statusb
Her2+, n47374532
RR (95% CI)c1.000.86 (0.55–1.36)1.31 (0.84–2.04)1.19 (0.73–1.94)0.28
Her2, n168153189131
RR (95% CI)c1.001.06 (0.82–1.36)1.57 (1.22–2.03)1.34 (1.01–1.77)0.01
Luminal A/luminal Bb
Luminal A, n898810080
RR (95% CI)c1.001.09 (0.78–1.50)1.46 (1.05–2.03)1.42 (1.00–2.02)0.03
Luminal B, n52426138
RR (95% CI)c1.000.88 (0.57–1.35)1.53 (1.02–2.30)1.18 (0.75–1.87)0.22
Tumor sizeb
Tumor ≤2 cm, n264232263191
RR (95% CI)c1.001.02 (0.82–1.26)1.43 (1.15–1.78)1.33 (1.05–1.69)0.004
Tumor >2 cm, n78739361
RR (95% CI)c1.001.13 (0.80–1.59)1.86 (1.33–2.60)1.54 (1.06–2.23)0.007
Gradeb
Low–intermediate grade, n264232261200
RR (95% CI)c1.001.02 (0.83–1.27)1.44 (1.16–1.79)1.39 (1.10–1.76)0.001
High grade, n15013515697
RR (95% CI)c1.001.08 (0.83–1.41)1.58 (1.21–2.06)1.27 (0.94–1.71)0.04
Lymph node statusb
Lymph node, n271238261192
RR (95% CI)c1.001.02 (0.83–1.26)1.40 (1.13–1.74)1.33 (1.05–1.68)0.005
Lymph node+, n60558554
RR (95% CI)c1.001.08 (0.73–1.59)2.12 (1.47–3.05)1.63 (1.08–2.44)0.004
  • aPtrend determined using the median values of the quartiles as a continuous term.

  • bPheterogeneity comparing in situ versus invasive = 0.81; by ductal versus lobular = 0.56; by ER/PR status = 0.04; by HER2 status = 0.56, by luminal type = 0.62, by tumor size = 0.49, by grade = 0.46, and by lymph node status = 0.16.

  • cUnconditional logistic regression models to calculate RR and 95% CI, adjusting for age at blood draw (continuous), date of blood draw (continuous), fasting status and time of day of blood draw (fasting and morning, other), PMH use at blood draw (yes, no), BMI at blood draw (continuous), age at menarche (continuous), history of BBD (yes, no), family history of breast cancer (yes, no), age at menopause (continuous), average childhood body size at ages 5 and 10 (continuous), and cohort (NHS, NHSII).