Table 2.
Study population and tumor characteristics by ER status in the NHS and the NHSII
| ER+ tumors N = 471 |
ER- tumors N = 127 |
|||
|---|---|---|---|---|
| Mean | SD | Mean | SD | |
| Age at diagnosis, years | 61.4 | 9.6 | 59.1 | 8.9 |
| BMI at diagnosis, kg/m2 | 26.0 | 5.0 | 26.1 | 5.1 |
| Parity | 2.6 | 1.8 | 2.9 | 1.8 |
| Recent alcohol, g/day | 6.5 | 11.7 | 5.8 | 10.0 |
| Cumulative average alcohol, g/day | 6.4 | 9.5 | 5.5 | 8.2 |
| N | % | N | % | |
| First-degree family history | 79 | 16.8 | 16 | 12.6 |
| Year of diagnosis | ||||
| 1990‒1999 | 251 | 53.3 | 91 | 71.7 |
| 2000 − 2004 | 182 | 38.6 | 26 | 20.5 |
| 2005‒2009 | 38 | 8.1 | 10 | 7.9 |
| Tumor size | ||||
| 0.1‒2.0 cm | 365 | 77.5 | 68 | 53.5 |
| 2.1‒4.0 cm | 75 | 15.9 | 46 | 36.2 |
| > 4.0 cm | 23 | 4.9 | 7 | 5.5 |
| Unknown | 8 | 1.7 | 6 | 4.7 |
| Lymph node involvement | ||||
| None | 349 | 74.1 | 95 | 74.8 |
| 1‒3 positive nodes | 85 | 18.0 | 22 | 17.3 |
| > 3 positive nodes | 33 | 7.0 | 8 | 6.3 |
| Metastatic at diagnosis | 4 | 0.8 | 1 | 0.8 |
| Unknown | 0 | 0 | 1 | 0.8 |
| Grade | ||||
| Well-differentiated | 124 | 26.3 | 6 | 4.7 |
| Moderately differentiated | 243 | 51.6 | 35 | 27.6 |
| Poorly differentiated | 89 | 18.9 | 67 | 52.8 |
| Unknown | 15 | 3.2 | 19 | 15.0 |
| Stagea | ||||
| I | 305 | 64.8 | 57 | 44.9 |
| II | 122 | 25.9 | 59 | 46.5 |
| III | 40 | 8.5 | 9 | 7.1 |
| IV | 4 | 0.8 | 1 | 0.8 |
| Unknown | 0 | 0 | 1 | 0.8 |
ER estrogen receptor, NHS Nurses’ Health Study, BMI body mass index
aStaging was based on tumor size and lymph node involvement