Table 4. Characteristics and standardised mean differences of covariates among patients with or without PMRT before and after propensity-score matching.
| Characteristics | Before matching (n = 1560) | After mathching (n = 1046) | ||||
|---|---|---|---|---|---|---|
| No PMRT (%) | PMRT (%) | Std. mean difference | No PMRT (%) | PMRT (%) | Std. mean difference | |
| Age, years | ||||||
| ≤40 | 21.8 | 22.5 | 0.017 | 22.0 | 22.7 | 0.018 |
| 41-60 | 58.7 | 60.3 | 0.032 | 58.5 | 60.4 | 0.039 |
| >60 | 19.5 | 17.2 | −0.060 | 19.5 | 16.9 | −0.069 |
| Race | ||||||
| White | 75.2 | 76.7 | 0.036 | 75.7 | 74.0 | −0.041 |
| Black | 18.4 | 17.9 | −0.012 | 18.4 | 20.5 | 0.055 |
| Asian or other | 6.4 | 5.3 | −0.047 | 5.9 | 5.5 | −0.017 |
| Insurance status | ||||||
| Not insured | 5.1 | 5.6 | 0.054 | 5.7 | 5.3 | 0.017 |
| Private insurance | 66.4 | 68.9 | 0.020 | 66.9 | 67.7 | −0.017 |
| Public insurance | 28.5 | 25.5 | −0.069 | 27.4 | 27.0 | −0.009 |
| Chalson/Deyo score | ||||||
| 0 | 84.0 | 88.3 | 0.132 | 87.6 | 87.2 | −0.012 |
| 1 | 6.7 | 9.2 | 0.086 | 7.5 | 8.6 | 0.040 |
| 2 | 1.5 | 0.8 | −0.085 | 1.1 | 1.1 | 0.000 |
| Unknown | 7.8 | 1.8 | −0.454 | 3.8 | 3.1 | −0.058 |
| Year of diagnosis | ||||||
| 1998-2003 | 13.7 | 6.2 | −0.311 | 9.2 | 8.6 | −0.024 |
| 2004-2009 | 86.3 | 93.8 | 0.311 | 90.8 | 91.4 | 0.024 |
| Histological type | ||||||
| Ductal | 82.2 | 79.6 | −0.064 | 81.2 | 81.4 | 0.005 |
| Lobular | 7.6 | 6.7 | −0.039 | 7.3 | 7.3 | 0.000 |
| Other | 10.2 | 13.7 | 0.103 | 11.5 | 11.3 | −0.006 |
| No. of nodes examined | ||||||
| 1-10 | 49.8 | 42.9 | −0.140 | 49.0 | 45.1 | −0.077 |
| >10 | 50.2 | 57.1 | 0.140 | 51.0 | 54.9 | 0.077 |
| Clinical T-stage | ||||||
| T1 | 12.0 | 6.1 | −0.248 | 8.8 | 8.6 | −0.008 |
| T2 | 42.0 | 28.1 | −0.309 | 39.0 | 39.2 | 0.004 |
| T3 | 25.9 | 30.9 | 0.109 | 28.5 | 27.9 | −0.012 |
| T4 | 20.1 | 34.9 | 0.310 | 23.7 | 24.3 | 0.012 |
| Clinical N-stage | ||||||
| N1 | 80.7 | 72.1 | −0.191 | 76.9 | 76.9 | 0.000 |
| N2 | 13.7 | 17.8 | 0.108 | 16.0 | 14.5 | −0.040 |
| N3 | 5.6 | 10.1 | 0.148 | 7.1 | 8.6 | 0.051 |
| Clinical AJCC stage | ||||||
| II | 49.5 | 25.6 | −0.547 | 41.9 | 40.3 | −0.035 |
| III | 50.5 | 74.4 | 0.547 | 58.1 | 59.7 | 0.035 |
| Pathologic T-stage (after NAC) | ||||||
| T0/Tis | 42.2 | 44.2 | 0.041 | 43.2 | 40.9 | −0.046 |
| T1 | 33.6 | 34.9 | 0.026 | 33.7 | 34.0 | 0.008 |
| T2 | 24.2 | 20.9 | −0.080 | 23.1 | 25.1 | 0.047 |
| Histologic grade | ||||||
| Well | 2.7 | 2.7 | −0.005 | 2.5 | 2.9 | 0.024 |
| Moderatedly | 25.3 | 22.1 | −0.075 | 26.0 | 25.6 | −0.009 |
| Poorly or undifferentiated | 72.0 | 75.2 | 0.074 | 71.5 | 71.5 | 0.000 |
| ER* | ||||||
| Negative | 50.2 | 55.7 | 0.110 | 53.7 | 51.8 | −0.038 |
| Positive | 31.7 | 36.7 | 0.104 | 34.6 | 37.1 | 0.052 |
| Unknown | 18.1 | 7.6 | −0.394 | 11.7 | 11.1 | −0.022 |
| PR* | ||||||
| Negative | 57.7 | 62.3 | 0.096 | 61.2 | 59.5 | −0.035 |
| Positive | 24.2 | 29.9 | 0.124 | 27.2 | 29.2 | 0.046 |
| Unknown | 18.1 | 7.8 | −0.387 | 11.6 | 11.3 | −0.014 |
| Chemotherapy type | ||||||
| Single-agent | 3.0 | 0.5 | −0.391 | 0.6 | 0.8 | 0.029 |
| Multi-agent | 97.0 | 99.5 | 0.391 | 99.4 | 99.2 | −0.029 |
Abbreviations: PMRT, postmastectomy radiotherapy; NS, not significant (P >0.05);
AJCC, American Joint Committee on Cancer (fifth or sixth edition); NAC, neoadjuvant chemotherapy; ER, estrogen receptor; PR, progesterone receptor
*
ER or PR groups include those with borderline results.