Table 3.
Age and age-standardised characteristics of breast cancer cases, Nurses' Health Study (1976 to 1996)
| Risk factors | DCIS (n = 272) | Invasive (n = 2249) |
| Means | ||
| Age at diagnosis, y | 57.9 | 57.3 |
| Age at menopause, y | 45.2 | 45.5 |
| Age at menarche, y | 12.3 | 12.4 |
| Body mass index at age 18, kg/m2 | 20.9 | 21.0 |
| Paritya | 3.1 | 3.2 |
| Age at first birtha, y | 24.9 | 25.4 |
| Alcohol, g/week | 5.7 | 6.3 |
| Frequency, % | ||
| Family history of breast cancer | 19.0 | 13.3 |
| Nulliparous | 6.9 | 6.9 |
| Premenopausal at diagnosis | 22.4 | 20.8 |
| Postmenopausal at diagnosis | 76.2 | 77.2 |
| Prior benign breast disease | 57.0 | 44.8 |
| Current postmenopausal hormone useb | 37.3 | 31.9 |
| Molecular Markers, % | ||
| ER positive | 74.0 | 77.0 |
| PR positive | 59.9 | 64.4 |
| HER2 positive | 27.2 | 10.9 |
aAmong parous women only. bAmong postmenopausal women only. DCIS, ductal carcinoma in situ; ER, oestrogen receptor; HER2, human epidermal growth factor receptor 2; PR, progesterone receptor.