Table 1.
Baseline characteristics of patients with BMBC in the training and validation cohort.
| Characteristic | Training cohort (n = 2632) | Validation cohort (n = 1744) | P∗ value | ||
| Number of patients | % | Number of patients | % | ||
| Age (years) | 0.232 | ||||
| Median (IQR) | 58 (49–66) | 58 (48–66) | |||
| Race | 0.496 | ||||
| White | 1984 | 75.4 | 1306 | 74.9 | |
| Black | 450 | 17.1 | 290 | 16.6 | |
| Other | 198 | 7.5 | 148 | 8.5 | |
| Marital status | 0.863 | ||||
| Married | 1315 | 50.0 | 876 | 50.2 | |
| USDW | 1317 | 50.0 | 868 | 49.8 | |
| T stage | 0.872 | ||||
| T0-T1 | 319 | 12.1 | 223 | 12.8 | |
| T2 | 932 | 35.4 | 600 | 34.4 | |
| T3 | 506 | 19.2 | 338 | 19.4 | |
| T4 | 875 | 33.2 | 583 | 33.4 | |
| Clinical nodal status | 0.919 | ||||
| Negative | 549 | 20.9 | 366 | 21.0 | |
| Positive | 2083 | 79.1 | 1378 | 79.0 | |
| Histology | 0.779 | ||||
| IDC | 2306 | 87.6 | 1523 | 87.3 | |
| ILC | 326 | 12.4 | 221 | 12.7 | |
| Grade | 0.139 | ||||
| I | 205 | 7.8 | 163 | 9.3 | |
| II | 1254 | 47.6 | 796 | 45.6 | |
| III | 1159 | 44.0 | 780 | 44.7 | |
| IV | 14 | 0.5 | 5 | 0.3 | |
| ER | 0.407 | ||||
| Negative | 477 | 18.1 | 299 | 17.1 | |
| Positive | 2155 | 81.9 | 1445 | 82.9 | |
| PR | 0.709 | ||||
| Negative | 829 | 31.5 | 540 | 31.0 | |
| Positive | 1803 | 68.5 | 1204 | 69.0 | |
| HER2 | 0.593 | ||||
| Negative | 1981 | 75.3 | 1325 | 76.0 | |
| Positive | 651 | 24.7 | 419 | 24.0 | |
| Brain metastasis | 0.763 | ||||
| No | 2460 | 93.5 | 1626 | 93.2 | |
| Yes | 172 | 6.5 | 118 | 6.8 | |
| Liver metastasis | 0.553 | ||||
| No | 2044 | 77.7 | 1341 | 76.9 | |
| Yes | 588 | 22.3 | 403 | 23.1 | |
| Lung metastasis | 0.273 | ||||
| No | 1975 | 75.0 | 1334 | 76.5 | |
| Yes | 657 | 25.0 | 410 | 23.5 | |
| Breast surgery | 0.631 | ||||
| No | 1658 | 63.0 | 1123 | 64.4 | |
| Breast-conserving surgery | 296 | 11.2 | 186 | 10.7 | |
| Mastectomy | 678 | 25.8 | 435 | 24.9 | |
| Distant surgery | 0.699 | ||||
| No | 2550 | 96.9 | 1686 | 96.7 | |
| Yes | 82 | 3.1 | 58 | 3.3 | |
| Chemotherapy | 0.003 | ||||
| No | 970 | 36.9 | 720 | 41.3 | |
| Yes | 1662 | 63.1 | 1024 | 58.7 | |
| Radiation therapy | 0.963 | ||||
| No | 1508 | 57.3 | 998 | 57.2 | |
| Yes | 1124 | 42.7 | 746 | 42.8 | |
ER = estrogen receptor, HER2 = human epidermal growth factor receptor 2, IDC = infiltrating ductal carcinoma, ILC = infiltrating lobular carcinoma, IQR = interquartile range, Other = American Indian/AK Native, Asian/Pacific Islander, P∗ = difference between the training and validation cohort, PR = progesterone receptor, Radiation therapy = beam radiation for breast or anterior chest wall, Tumor grade I = well differentiated, Tumor grade II = moderately differentiated, Tumor grade III = poorly differentiated, Tumor grade IV = undifferentiated, USDW = unmarried/separated/divorced/widowed.