Table 1.
Distributions of select characteristics by case–control status
| Variables | Cases (N = 658) | Controls (N = 866) | P valuea |
|---|---|---|---|
| Mean age (SD) (years) | 52.8 (11.1) | 52.5 (11.6) | 0.568 |
| Mean age at menarche (SD) (years)b | 15.1 (4.9) | 15.8 (4.6) | <0.05 |
| Estrogen receptor statusc | |||
| Positive | 316 (61.5) | ||
| Negative | 198 (38.5) | ||
| Progesterone receptor statusc | |||
| Positive | 350 (68.1) | ||
| Negative | 164 (31.9) | ||
| HER2 statusc | |||
| Positive | 198 (39.4) | ||
| Negative | 305 (60.6) | ||
| ALNM statusc | |||
| Positive | 284 (53.7) | ||
| Negative | 245 (46.3) | ||
a
Student's t‐test for the difference between cases and controls.
b
Age at menarche information was available in 632 breast cancer cases and 849 controls.
c
Information on estrogen receptor, progesterone receptor, epidermal growth factor receptor 2 (HER2) and axillary lymph node metastasis (ALNM) status was available in 514 (78.1%), 514 (78.1%), 503 (76.4%) and 529 (80.4%) patients, respectively.