Table 1. Baseline characteristics of the study population before PSM.
| Variables | All patients | Non-surgery group | Surgery group | P value | |||||
|---|---|---|---|---|---|---|---|---|---|
| N=7,255 | % | N=4,508 | % | N=2,747 | % | ||||
| Age (years), mean ± SD | 59.5±14.2 | 60.5±14.1 | 57.9±14.2 | <0.001 | |||||
| Age (years) | <0.001 | ||||||||
| 18–39 | 626 | 8.6 | 330 | 7.3 | 296 | 10.8 | |||
| 40–59 | 3,053 | 42.1 | 1,829 | 40.6 | 1,224 | 44.6 | |||
| ≥60 | 3,576 | 49.3 | 2,349 | 52.1 | 1,227 | 44.7 | |||
| Race | 0.64 | ||||||||
| White | 5,423 | 74.7 | 3,360 | 74.5 | 2,063 | 75.1 | |||
| Black | 1,252 | 17.3 | 792 | 17.6 | 460 | 16.7 | |||
| Other | 580 | 8.0 | 356 | 7.9 | 224 | 8.2 | |||
| Cohabitation status | <0.001 | ||||||||
| Non-cohabitation | 3,824 | 52.7 | 2,503 | 55.5 | 1,321 | 48.1 | |||
| Cohabitation | 3,431 | 47.3 | 2,005 | 44.5 | 1,426 | 51.9 | |||
| Education | <0.001 | ||||||||
| Low | 3,385 | 46.7 | 2,186 | 48.5 | 1,199 | 43.6 | |||
| High | 3,870 | 53.3 | 2,322 | 51.5 | 1,548 | 56.4 | |||
| Income | <0.001 | ||||||||
| Low | 3,943 | 54.3 | 2,380 | 52.8 | 1,563 | 56.9 | |||
| High | 3,312 | 45.7 | 2,128 | 47.2 | 1,184 | 43.1 | |||
| Year of diagnosis | <0.001 | ||||||||
| 2010–2012 | 3,361 | 46.3 | 1,878 | 41.7 | 1,483 | 54.0 | |||
| 2013–2015 | 3,894 | 53.7 | 2,630 | 58.3 | 1,264 | 46.0 | |||
| Tumor grade | <0.001 | ||||||||
| Well/moderately differentiated | 2,424 | 53.8 | 1,128 | 41.1 | 2,424 | 53.8 | |||
| Poorly/un-differentiated | 2,084 | 46.2 | 1,619 | 58.9 | 2,084 | 46.2 | |||
| Histotype | 0.24 | ||||||||
| IDC | 5,731 | 79.0 | 3,572 | 79.2 | 2,159 | 78.6 | |||
| ILC | 626 | 8.6 | 399 | 8.9 | 227 | 8.3 | |||
| Others | 898 | 12.4 | 537 | 11.9 | 361 | 13.1 | |||
| Tumor size (cm) | 0.023 | ||||||||
| (0–2] | 1,073 | 14.8 | 707 | 15.7 | 366 | 13.3 | |||
| (2–5] | 3,438 | 47.4 | 2,110 | 46.8 | 1,328 | 48.3 | |||
| >5 | 2,744 | 37.8 | 1,691 | 37.5 | 1,053 | 38.3 | |||
| Lymph node status | <0.001 | ||||||||
| Negative | 1,477 | 20.4 | 1,042 | 23.1 | 435 | 15.8 | |||
| Positive | 5,778 | 79.6 | 3,466 | 76.9 | 2,312 | 84.2 | |||
| ER status | <0.001 | ||||||||
| Positive | 5,382 | 74.2 | 3,428 | 76.0 | 1,954 | 71.1 | |||
| Negative | 1873 | 25.8 | 1,080 | 24.0 | 793 | 28.9 | |||
| PR status | <0.001 | ||||||||
| Positive | 4,365 | 60.2 | 2,791 | 61.9 | 1,574 | 57.3 | |||
| Negative | 2,890 | 39.8 | 1,717 | 38.1 | 1,173 | 42.7 | |||
| HER2 status | 0.79 | ||||||||
| Positive | 1,968 | 27.1 | 1,218 | 27.0 | 750 | 27.3 | |||
| Negative | 5,287 | 72.9 | 3,290 | 73.0 | 1,997 | 72.7 | |||
| Molecular subtype | <0.001 | ||||||||
| HR+/HER2+ | 1,294 | 17.8 | 810 | 18.0 | 484 | 17.6 | |||
| HR−/HER2+ | 674 | 9.3 | 408 | 9.1 | 266 | 9.7 | |||
| HR+/HER2− | 4,210 | 58.0 | 2,695 | 59.8 | 1,515 | 55.2 | |||
| TN | 1,077 | 14.8 | 595 | 13.2 | 482 | 17.5 | |||
| Bone metastasis | <0.001 | ||||||||
| Yes | 4,977 | 68.6 | 3,242 | 71.9 | 1,735 | 63.2 | |||
| No | 2,278 | 31.4 | 1,266 | 28.1 | 1,012 | 36.8 | |||
| Brain metastasis | <0.001 | ||||||||
| Yes | 503 | 6.9 | 389 | 8.6 | 114 | 4.1 | |||
| No | 6,752 | 93.1 | 4,119 | 91.4 | 2,633 | 95.9 | |||
| Liver metastasis | <0.001 | ||||||||
| Yes | 2,007 | 27.7 | 1,386 | 30.7 | 621 | 22.6 | |||
| No | 5,248 | 72.3 | 3,122 | 69.3 | 2,126 | 77.4 | |||
| Lung metastasis | <0.001 | ||||||||
| Yes | 2,380 | 32.8 | 1,634 | 36.2 | 746 | 27.2 | |||
| No | 4,875 | 67.2 | 2,874 | 63.8 | 2,001 | 72.8 | |||
| Chemotherapy | <0.001 | ||||||||
| No/unknown | 2,874 | 39.6 | 2,034 | 45.1 | 840 | 30.6 | |||
| Yes | 4,381 | 60.4 | 2,474 | 54.9 | 1,907 | 69.4 | |||
| Radiotherapy | <0.001 | ||||||||
| No/unknown | 4,679 | 64.5 | 3,189 | 70.7 | 1,490 | 54.2 | |||
| Yes | 2,576 | 35.5 | 1,319 | 29.3 | 1,257 | 45.8 | |||
PSM, propensity score matching; SD, standard deviation; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor-2; HR, hormone receptor; TN, triple-negative (HR−HER2−).