Table 2. Baseline characteristics after PSM.
| Variables | Non-surgery group | Surgery group | P value | |||
|---|---|---|---|---|---|---|
| N=2,288 | % | N=2,288 | % | |||
| Age (years), mean ± SD | 59.1±13.7 | 58.8±14.3 | 0.48 | |||
| Age (years) | 0.139 | |||||
| 18–39 | 191 | 8.3 | 226 | 9.9 | ||
| 40–59 | 1,015 | 44.4 | 971 | 42.4 | ||
| ≥60 | 1,082 | 47.3 | 1,091 | 47.7 | ||
| Race | 0.534 | |||||
| White | 1,727 | 75.5 | 1,721 | 75.2 | ||
| Black | 395 | 17.3 | 382 | 16.7 | ||
| Other | 166 | 7.3 | 185 | 8.1 | ||
| Cohabitation status | 0.679 | |||||
| Non-cohabitation | 1,140 | 49.8 | 1,155 | 50.5 | ||
| Cohabitation | 1,148 | 50.2 | 1,133 | 49.5 | ||
| Education | 0.812 | |||||
| Low | 1,004 | 43.9 | 1,013 | 44.3 | ||
| High | 1,284 | 56.1 | 1,275 | 55.7 | ||
| Income | 0.613 | |||||
| Low | 1,294 | 56.6 | 1,276 | 55.8 | ||
| High | 994 | 43.4 | 1,012 | 44.2 | ||
| Year of diagnosis | 0.375 | |||||
| 2010–2012 | 1,167 | 51.0 | 1,136 | 49.7 | ||
| 2013–2015 | 1,121 | 49.0 | 1,152 | 50.3 | ||
| Tumor grade | 0.721 | |||||
| Well/moderately differentiated | 1,026 | 44.8 | 1,013 | 44.3 | ||
| Poorly/un-differentiated | 1,262 | 55.2 | 1,275 | 55.7 | ||
| Histotype | 0.659 | |||||
| IDC | 1,814 | 79.3 | 1,789 | 78.2 | ||
| ILC | 187 | 8.2 | 199 | 8.7 | ||
| Others | 287 | 12.5 | 300 | 13.1 | ||
| Tumor size (cm) | 0.846 | |||||
| (0–2] | 329 | 14.4 | 329 | 14.4 | ||
| (2–5] | 1,077 | 47.1 | 1,095 | 47.9 | ||
| >5 | 882 | 38.5 | 864 | 37.8 | ||
| Lymph node status | 0.36 | |||||
| Negative | 434 | 19.0 | 409 | 17.9 | ||
| Positive | 1,854 | 81.0 | 1,879 | 82.1 | ||
| Molecular subtype | 0.85 | |||||
| HR+/HER2+ | 391 | 17.1 | 408 | 17.8 | ||
| HR−/HER2+ | 227 | 9.9 | 216 | 9.4 | ||
| HR+/HER2− | 1,307 | 57.1 | 1,293 | 56.5 | ||
| TN | 363 | 15.9 | 371 | 16.2 | ||
| Bone metastasis | 1 | |||||
| Yes | 1,512 | 66.1 | 1,511 | 66.0 | ||
| No | 776 | 33.9 | 777 | 34.0 | ||
| Brain metastasis | 0.674 | |||||
| Yes | 103 | 4.5 | 110 | 4.8 | ||
| No | 2,185 | 95.5 | 2,178 | 95.2 | ||
| Liver metastasis | 0.676 | |||||
| Yes | 531 | 23.2 | 544 | 23.8 | ||
| No | 1,757 | 76.8 | 1,744 | 76.2 | ||
| Lung metastasis | 0.625 | |||||
| Yes | 653 | 28.5 | 669 | 29.2 | ||
| No | 1,635 | 71.5 | 1,619 | 70.8 | ||
| Chemotherapy | 0.459 | |||||
| No/unknown | 828 | 36.2 | 803 | 35.1 | ||
| Yes | 1,460 | 63.8 | 1,485 | 64.9 | ||
| Radiotherapy | 0.359 | |||||
| No/unknown | 1,454 | 63.5 | 1,423 | 62.2 | ||
| Yes | 834 | 36.5 | 865 | 37.8 | ||
PSM, propensity score matching; SD, standard deviation; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; HR, hormone receptor; HER2, human epidermal growth factor receptor-2; TN, triple-negative (HR−HER2−).