Table 2 Case-case ORs of tumor characteristics by age among premenopausal cases in Carolina Breast Cancer Study phases I–III (n = 2373)
|  | Age <40 years | Age ≥40 years (reference) | |
|---|---|---|---|
Tumor characteristic | n (%) | OR (95Â % CI) | n (%) |
Mean age (±SD) | 34.8 (±3.7) |  | 45.4 (±3.5) |
Stage | |||
 In situ | 35 (5.4) | 0.98 (0.65–1.49) | 125 (7.5) |
 Stage I | 163 (25.3) | 1.0 | 573 (34.5) |
 Stage II | 340 (52.7) | 1.74 (1.40–2.16) | 687 (41.4) |
 Stage III | 84 (13.0) | 1.34 (0.99–1.82) | 220 (13.3) |
 Stage IV | 23 (3.6) | 1.47 (0.88–2.46) | 55 (3.3) |
 Missing | 19 |  | 51 |
Subtypea | |||
 Luminal | 106 (52.0) | 1.0 | 283 (65.2) |
 Basal-like | 51 (25.0) | 1.87 (1.22–2.84) | 73 (16.8) |
 HER2 | 18 (8.8) | 1.72 (0.91–3.23) | 28 (6.5) |
 Unclassified | 29 (14.2) | 1.55 (0.93–2.58) | 50 (11.5) |
 Missing | 109 |  | 286 |
ER status | |||
 Negative | 270 (44.9) | 1.0 | 515 (33.4) |
 Positive | 332 (55.1) | 0.62 (0.51–0.75) | 1028 (66.6) |
 Missingb | 62 |  | 168 |
PR status | |||
 Negative | 302 (53.6) | 1.0 | 544 (37.6) |
 Positive | 261 (46.4) | 0.52 (0.43–0.63) | 903 (62.4) |
 Missingb | 101 |  | 264 |
HER2 statusa | |||
 Negative | 194 (77.0) | 1.0 | 447 (82.3) |
 Positive | 58 (23.0) | 1.39 (0.96–2.01) | 96 (17.7) |
 Missing | 61 |  | 177 |
Histologic gradec | |||
 Well-differentiated/moderate differentiation | 89 (21.3) | 1.0 | 268 (25.6) |
 Poor differentiation | 328 (78.7) | 1.27 (0.97–1.66) | 779 (74.4) |
 Missingb | 82 |  | 238 |
Nuclear gradec | |||
 Slight/moderate pleomorphism | 174 (41.2) | 1.0 | 557 (52.2) |
 Marked pleomorphism | 248 (58.8) | 1.55 (1.24–1.95) | 511 (47.8) |
 Missingc | 77 |  | 217 |
Node status | |||
 Negative | 329 (53.4) | 1.0 | 907 (58.4) |
 Positive | 287 (46.6) | 1.23 (1.02–1.48) | 645 (41.6) |
 Missingb | 48 |  | 159 |
Tumor size | |||
 ≤ 2 cm | 233 (38.4) | 1.0 | 749 (48.8) |
 > 2 cm | 373 (61.6) | 1.53 (1.26–1.85) | 786 (51.2) |
 Missingb | 58 |  | 176 |