TABLE 1.
Patient, tumor, and treatment characteristics of the study cohort by age group (categorical data presented as n (%), and continuous data presented as median [interquartile range])
| Characteristic | Entire cohort | Age ≤ 40 years | Age 41–60 years | Age ≥ 61 years | p |
|---|---|---|---|---|---|
| n = 1383 | n = 300 | n = 772 | n = 311 | ||
| Age, years | 50 (42–59) | 36 (32–38) | 50 (46–55) | 66 (63–70) | < 0.001 |
| Tumor size, cm | 4.0 (2.5–6.0) | 4.0 (3.0–6.0) | 4.0 (2.5–6.0) | 3.9 (2.8–6.0) | 0.80 |
| Race | |||||
| White | 849 (66.6%) | 168 (61%) | 467 (66%) | 214 (74%) | 0.005 |
| Black | 194 (15%) | 39 (14%) | 117 (16%) | 38 (13%) | |
| Asian/Pacific Islander | 149 (12%) | 39 (14%) | 82 (12%) | 28 (10%) | |
| Other | 83 (6.5%) | 28 (10%) | 46 (6%) | 9 (3%) | |
| Unknown | 108 | 26 | 60 | 22 | |
| Clinical tumor stage | < 0.001 | ||||
| T0 (Occult) | 11 (0.8%) | 2 (0.7%) | 5 (0.60%) | 4 (1.3%) | |
| T1 | 197 (14%) | 42 (14%) | 110 (14%) | 45 (14%) | |
| T2 | 766 (55%) | 167 (56%) | 423 (55%) | 176 (57%) | |
| T3 | 271 (20%) | 74 (25%) | 156 (20%) | 41 (13%) | |
| T4 | 136 (9.8%) | 14 (4.7%) | 78 (10%) | 44 (14%) | |
| Clinical nodal stage | > 0.90 | ||||
| N0 | 449 (32%) | 97 (32%) | 255 (33%) | 97 (31%) | |
| N1 | 813 (59%) | 180 (60%) | 447 (58%) | 186 (60%) | |
| N2-N3 | 121 (8.7%) | 23 (7.7%) | 70 (9.1%) | 28 (9.0%) | |
| Histology | 0.001 | ||||
| Ductal | 1244 (92%) | 287 (97%) | 687 (91%) | 270 (89%) | |
| Lobular or mixed | 99 (7.3%) | 7 (2.4%) | 63 (8.3%) | 29 (9.5%) | |
| Other | 16 (1.2%) | 2 (0.7%) | 8 (1.1%) | 6 (2.0%) | |
| Unknown | 24 | 4 | 14 | 6 | |
| Histologic grade | 0.034 | ||||
| Well differentiated | 21 (1.5%) | 0 (0%) | 14 (1.8%) | 7 (2.3%) | |
| Moderately differentiated | 391 (28%) | 78 (26%) | 216 (28%) | 97 (31%) | |
| Poorly differentiated | 964 (70%) | 221 (74%) | 536 (70%) | 207 (67%) | |
| Lymphovascular invasion | 406 (39%) | 96 (42%) | 226 (38%) | 84 (36%) | 0.40 |
| Unknown | 7 | 1 | 6 | 0 | |
| Tumor subtype | 0.60 | ||||
| HR+/HER2− | 487 (35%) | 106 (35%) | 271 (35%) | 110 (35%) | |
| HER2+ | 502 (36%) | 111 (37%) | 269 (35%) | 122 (40%) | |
| TN | 394 (28.5%) | 83 (28%) | 232 (30%) | 79 (25%) | |
| BRCA1/2 mutation status | < 0.001 | ||||
| Positive | 98 (11%) | 46 (18%) | 49 (9.8%) | 3 (2.6%) | |
| Negative | 672 (77%) | 207 (79%) | 401 (80%) | 64 (55%) | |
| Unknown result or VUS | 108 (12%) | 9 (3.4%) | 50 (10%) | 49 (42%) | |
| Not tested/missing | 505 | 38 | 272 | 195 | |
| Pathologic tumor stage | 0.57 | ||||
| T0 | 399 (29%) | 97 (33%) | 219 (29%) | 82 (27%) | |
| Tis | 99 (7.2%) | 21 (7.0%) | 58 (7.6%) | 19 (6.2%) | |
| T1 | 574 (42%) | 125 (42%) | 324 (42%) | 125 (41%) | |
| T2 | 232 (17%) | 44 (15%) | 124 (16%) | 64 (21%) | |
| T3 | 59 (4.3%) | 10 (3.4%) | 36 (4.7%) | 13 (4.2%) | |
| T4 | 11 (0.80%) | 1 (0.30%) | 6 (0.80%) | 4 (1.3%) | |
| Not assessed or occult | 11 | 2 | 5 | 4 | |
| Pathologic nodal stage | 0.20 | ||||
| N0 | 828 (60%) | 188 (63%) | 460 (60%) | 180 (58%) | |
| N1 | 344 (25%) | 81 (27%) | 191 (25%) | 72 (23%) | |
| N2-N3 | 208 (15%) | 30 10%) | 121 (16%) | 57 (18%) | |
| Neoadjuvant chemotherapy | < 0.001 | ||||
| ACT based | 1268 (92%) | 286 (95%) | 722 (94%) | 260 (84%) | |
| Taxane based | 95 (6.9%) | 14 (4.7%) | 42 (5.5%) | 39 (13%) | |
| CMF | 9 (0.7%) | 0 (0%) | 0 (0%) | 9 (2.9%) | |
| Other | 5 (0.4%) | 0 (0%) | 3 (0.4%) | 2 (0.6%) | |
| NAC included carboplatin | 172 (12%) | 47 (16%) | 98 (13%) | 27 (8.7%) | 0.029 |
| Final breast surgerya | < 0.001 | ||||
| BCS | 586 (43%) | 88 (30%) | 332 (43%) | 166 (54%) | |
| Unilateral mastectomy | 388 (28%) | 62 (21%) | 210 (27%) | 116 (38%) | |
| Bilateral mastectomy | 398 (29%) | 148 (50%) | 225 (29%) | 25 (8.1%) | |
| Final axillary surgery | |||||
| SLNB | 722 (52%) | 186 (62%) | 393 (51%) | 149 (48%) | < 0.001 |
| ALND | 661 (48%) | 114 (38%) | 379 (49%) | 162 (52%) | < 0.001 |
a
11 patients with occult primary breast cancer did not undergo primary breast surgery
HR hormone receptor, HER2 human epidermal growth factor receptor 2, TN triple-negative, BRCA1/2 breast cancer gene 1 or 2, VUS variant of unknown significance, ACT doxorubicin and cyclophosphamide followed by a taxane CMF cyclophosphamide, methotrexate, 5-fluorouracil, pCR pathologic complete response, NAC neoadjuvant chemotherapy, BCS breast-conserving surgery, SLNB sentinel lymph node biopsy, ALND axillary lymph node dissection