Table 1.
Risk factor distributions
| Risk factor | Controls (n = 2990) | Cases (n = 551) |
|---|---|---|
| Age (range) | 47 (20,55) | 47 (24,55) |
| White race (%) | 87% | 93% |
| Premenopausal BMI, median (range) | 23 (16,55) | 23 (16,44) |
| Postmenopausal BMI, median (range) | 24 (16,62) | 24 (17,35) |
| Family history of breast cancer | 7% | 13% |
| Prior benign breast disease | 12% | 18% |
| Age at menarche, median (range) | 13 (8,20) | 12 (8,18) |
| Nulliparity | 14% | 15% |
| Number of children, median (range) | 3 (1,13) | 3 (1,9) |
| Age at first birth, median (range) | 23 (11,43) | 23 (13,40) |
| Months of breastfeeding, median (range) | 1 (0,168) | 1 (0.98) |
| Postmenopausal | 40% | 37% |
| Age at menopause, median (range) | 42 (21.53) | 42 (23,53) |
| Estrogen receptor positive by IHC1 | NA | 57% |
| Progesterone receptor positive by IHC1 | NA | 51% |
| ERBB2 (HER2) positive by IHC1 | NA | 21% |
BMI, body mass index; IHC, immunohistochemistry; ERBB2, human epidermal growth factor receptor.
1
33 cases are missing immunohistochemistry data.