Table 1 Selected baseline characteristics for the SEER database study population divided per study groups before and after PSM
Characteristics | Before PSM (2267) | After PSM (1066) | ||||
|---|---|---|---|---|---|---|
No RT | RT | P-value | No RT | RT | P-value | |
Age at diagnosis |  |  | < 0.05 |  |  | 0.057 |
 < 60 | 504 (42.7%) | 592 (54.5%) |  | 264 (49.5%) | 296 (55.5%) |  |
 ≥ 60 | 677 (57.3%) | 494 (45.5%) |  | 269 (50.5%) | 237 (44.5%) |  |
Ethnicity |  |  | < 0.05 |  |  | 0.667 |
 White | 929 (78.7%) | 825 (76.0%) |  | 402 (75.4%) | 408 (76.5%) |  |
 Black | 163 (13.8%) | 190 (17.5%) |  | 95 (17.8%) | 85 (15.9%) |  |
 Others | 89 (7.5%) | 71 (6.5%) |  | 36 (6.8%) | 40 (7.5%) |  |
Marital status | Â | Â | 0.263 | Â | Â | 0.736 |
 Single | 185 (15.7%) | 151 (13.9%) |  | 86 (16.1%) | 81 (15.2%) |  |
 Married | 996 (84.3%) | 935 (86.1%) |  | 447 (83.9%) | 452 (84.8%) |  |
Grade | Â | Â | 0.539 | Â | Â | 0.472 |
 G1 | 64 (5.4%) | 56 (5.2%) |  | 23 (4.3%) | 24 (4.5%) |  |
 G2 | 173 (14.6%) | 137 (12.6%) |  | 66 (12.4%) | 69 (12.9%) |  |
 G3 | 888 (75.2%) | 839 (77.3%) |  | 416 (78.0%) | 400 (75.0%) |  |
 G4 | 56 (4.7%) | 54 (5.0%) |  | 28 (5.3%) | 40 (7.5%) |  |
ER status | Â | Â | 0.413 | Â | Â | 0.456 |
 Negative | 979 (82.9%) | 885 (81.5%) |  | 451 (84.6%) | 441 (82.7%) |  |
 Positive | 202 (17.1%) | 201 (18.5%) |  | 82 (15.4%) | 92 (17.3%) |  |
PR status | Â | Â | 0.058 | Â | Â | 0.192 |
 Negative | 1044 (88.4%) | 930 (85.6%) |  | 475 (89.1%) | 460 (86.3%) |  |
 Positive | 137 (11.6%) | 156 (14.4%) |  | 58 (10.9%) | 73 (13.7%) |  |
Stage T |  |  | < 0.05 |  |  | 0.457 |
 ≤ 5 cm | 937 (79.3%) | 814 (75.0%) |  | 373 (70.0%) | 385 (72.2%) |  |
 > 5 cm | 244 (20.7%) | 272 (25.0%) |  | 160 (30.0%) | 148 (27.8%) |  |
Stage N | Â | Â | 0.090 | Â | Â | 0.202 |
 N0 | 929 (78.7%) | 811 (74.7%) |  | 381 (71.5%) | 382 (71.7%) |  |
 N1 | 173 (14.6%) | 195 (18.0%) |  | 96 (18.0%) | 112 (21.0%) |  |
 N2 | 51 (4.3%) | 45 (4.1%) |  | 35 (6.6%) | 22 (4.1%) |  |
 N3 | 28 (2.4%) | 35 (3.2%) |  | 21 (3.9%) | 17 (3.2%) |  |
Stage TNM |  |  | < 0.05 |  |  | 0.848 |
 I | 247 (20.9%) | 283 (26.1%) |  | 109 (20.5%) | 115 (21.6%) |  |
 II | 779 (66.0%) | 605 (55.7%) |  | 314 (58.9%) | 314 (58.9%) |  |
 III | 155 (13.1%) | 198 (18.2%) |  | 110 (20.6%) | 104 (19.5%) |  |
Breast operation |  |  | < 0.05 |  |  | 0.667 |
 Lumpectomy | 254 (21.5%) | 692 (63.7%) |  | 248 (46.5%) | 240 (45.0%) |  |
 Mastectomy | 927 (78.5%) | 394 (36.3%) |  | 285 (53.5%) | 293 (55.0%) |  |
Chemotherapy |  |  | < 0.05 |  |  | 0.111 |
 Not done/unknown | 548 (46.4%) | 254 (23.4%) |  | 176 (33.0%) | 151 (28.3%) |  |
 Done | 633 (53.6%) | 832 (76.6%) |  | 357 (67.0%) | 382 (71.7%) |  |
Axilla LN operation | Â | 0.050 | Â | Â | 0.425 | |
 SLNB | 581 (49.2%) | 580 (53.4%) |  | 261 (49.0%) | 247 (46.3%) |  |
 ALND | 600 (50.8%) | 506 (46.6%) |  | 272 (51.0%) | 286 (53.7%) |  |