Table 2

Results from weighted Cox regression analysis
Parameter
 All
 BRCA1 carriers
 BRCA2 carriers

UN
 BC
 HR
 95% CI
 UN
 BC
 HR
 95% CI
 UN
 BC
 HR
 95% CI
Parity











     Nulliparous
 37
 65
 1.00
25
 37
 1.00
12
 28
 1.00
     Parous
 295
 392
 0.54
 0.37–0.81
 193
 211
 0.53
 0.34–0.83
 102
 181
 0.58
 0.27–1.24
Parity by attained age











     ≤40 years











          Nulliparous
 28
 44
 1.00
21
 24
 1.00
7
 20
 1.00
          Parousa
 76
 127
 1.01
 0.58–1.76
 50
 76
 1.17
 0.55–2.52
 26
 51
 0.72
 0.42–1.24
     >40 years











          Nulliparous
 9
 21
 1.00
4
 13
 1.00
5
 8
 1.00
          Parous
 219
 265
 0.44
 0.23–0.84
 143
 135
 0.34
 0.16–0.70
 76
 130
 1.21
 0.37–3.92
Number of live birthsb











     Nulliparous
 37
 65
 1.00
25
 37
 1.00
12
 28
 1.00
     1
 46
 57
 0.62
 0.37–1.02
 27
 34
 0.62
 0.34–1.11
 19
 23
 0.58
 0.22–1.53
     2
 109
 167
 0.57
 0.38–0.86
 73
 80
 0.54
 0.33–0.87
 36
 87
 0.68
 0.31–1.47
     3
 66
 79
 0.64
 0.34–0.86
 42
 50
 0.56
 0.33–0.97
 24
 29
 0.44
 0.19–1.04
     4+
 56
 82
 0.55
 0.34–0.91
 42
 44
 0.51
 0.29–0.89
 14
 38
 0.71
 0.27–1.88
     Per live birth

0.90
 0.80–1.00

0.89
 0.78–1.01

0.93
 0.75–1.14
Age at first live birth











     <20 years
 61
 55
 1.00
38
 35
 1.00
23
 20
 1.00
     20–24 years
 132
 179
 1.16
 0.76–1.78
 85
 92
 1.08
 0.65–1.78
 47
 87
 1.74
 0.87–3.49
     25–29 years
 106
 108
 1.13
 0.72–1.79
 73
 66
 1.08
 0.64–1.52
 33
 42
 1.48
 0.68–3.22
     ≥ 30 years
 39
 50
 1.30
 0.74–2.29
 25
 18
 0.83
 0.42–1.64
 14
 32
 4.77
 2.08–10.94
     Nulliparous
 37
 65
 2.09
 1.26–3.45
 25
 37
 1.96
 1.10–3.52
 12
 28
 2.85
 1.13–7.15

UN, unaffected carriers; BC, breast cancer; HR, hazard ratio; CI, confidence interval. aAnalyses not adjusted for oophorectomy (all others adjusted). Overall analysis stratified by year of birth and gene. bAssuming that births between first and last birth were equally spaced; 25 carriers (7 affected, 18 unaffected) with missing age at last birth were assumed to be nulliparous until age at first birth and were then considered as a separate category (hazard ratios not shown).

Antoniou et al. Breast Cancer Research 2006 8:R72   doi:10.1186/bcr1630