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Table 1 Selected baseline characteristics for the SEER database study population divided per study groups before and after PSM

From: The role of radiotherapy in metaplastic breast cancer: a propensity score-matched analysis of the SEER database

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    0.263    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    0.539    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    0.413    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    0.058    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    0.090    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   0.050    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%)  
  1. SLNB Sentinel lymph node biopsy, ALND axillary lymph node dissection
  2. Significant results are in italic